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diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt deleted file mode 100644 index e3abfbd32f71..000000000000 --- a/Documentation/networking/bonding.txt +++ /dev/null @@ -1,2837 +0,0 @@ - - Linux Ethernet Bonding Driver HOWTO - - Latest update: 27 April 2011 - -Initial release : Thomas Davis <tadavis at lbl.gov> -Corrections, HA extensions : 2000/10/03-15 : - - Willy Tarreau <willy at meta-x.org> - - Constantine Gavrilov <const-g at xpert.com> - - Chad N. Tindel <ctindel at ieee dot org> - - Janice Girouard <girouard at us dot ibm dot com> - - Jay Vosburgh <fubar at us dot ibm dot com> - -Reorganized and updated Feb 2005 by Jay Vosburgh -Added Sysfs information: 2006/04/24 - - Mitch Williams <mitch.a.williams at intel.com> - -Introduction -============ - - The Linux bonding driver provides a method for aggregating -multiple network interfaces into a single logical "bonded" interface. -The behavior of the bonded interfaces depends upon the mode; generally -speaking, modes provide either hot standby or load balancing services. -Additionally, link integrity monitoring may be performed. - - The bonding driver originally came from Donald Becker's -beowulf patches for kernel 2.0. It has changed quite a bit since, and -the original tools from extreme-linux and beowulf sites will not work -with this version of the driver. - - For new versions of the driver, updated userspace tools, and -who to ask for help, please follow the links at the end of this file. - -Table of Contents -================= - -1. Bonding Driver Installation - -2. Bonding Driver Options - -3. Configuring Bonding Devices -3.1 Configuration with Sysconfig Support -3.1.1 Using DHCP with Sysconfig -3.1.2 Configuring Multiple Bonds with Sysconfig -3.2 Configuration with Initscripts Support -3.2.1 Using DHCP with Initscripts -3.2.2 Configuring Multiple Bonds with Initscripts -3.3 Configuring Bonding Manually with Ifenslave -3.3.1 Configuring Multiple Bonds Manually -3.4 Configuring Bonding Manually via Sysfs -3.5 Configuration with Interfaces Support -3.6 Overriding Configuration for Special Cases -3.7 Configuring LACP for 802.3ad mode in a more secure way - -4. Querying Bonding Configuration -4.1 Bonding Configuration -4.2 Network Configuration - -5. Switch Configuration - -6. 802.1q VLAN Support - -7. Link Monitoring -7.1 ARP Monitor Operation -7.2 Configuring Multiple ARP Targets -7.3 MII Monitor Operation - -8. Potential Trouble Sources -8.1 Adventures in Routing -8.2 Ethernet Device Renaming -8.3 Painfully Slow Or No Failed Link Detection By Miimon - -9. SNMP agents - -10. Promiscuous mode - -11. Configuring Bonding for High Availability -11.1 High Availability in a Single Switch Topology -11.2 High Availability in a Multiple Switch Topology -11.2.1 HA Bonding Mode Selection for Multiple Switch Topology -11.2.2 HA Link Monitoring for Multiple Switch Topology - -12. Configuring Bonding for Maximum Throughput -12.1 Maximum Throughput in a Single Switch Topology -12.1.1 MT Bonding Mode Selection for Single Switch Topology -12.1.2 MT Link Monitoring for Single Switch Topology -12.2 Maximum Throughput in a Multiple Switch Topology -12.2.1 MT Bonding Mode Selection for Multiple Switch Topology -12.2.2 MT Link Monitoring for Multiple Switch Topology - -13. Switch Behavior Issues -13.1 Link Establishment and Failover Delays -13.2 Duplicated Incoming Packets - -14. Hardware Specific Considerations -14.1 IBM BladeCenter - -15. Frequently Asked Questions - -16. Resources and Links - - -1. Bonding Driver Installation -============================== - - Most popular distro kernels ship with the bonding driver -already available as a module. If your distro does not, or you -have need to compile bonding from source (e.g., configuring and -installing a mainline kernel from kernel.org), you'll need to perform -the following steps: - -1.1 Configure and build the kernel with bonding ------------------------------------------------ - - The current version of the bonding driver is available in the -drivers/net/bonding subdirectory of the most recent kernel source -(which is available on http://kernel.org). Most users "rolling their -own" will want to use the most recent kernel from kernel.org. - - Configure kernel with "make menuconfig" (or "make xconfig" or -"make config"), then select "Bonding driver support" in the "Network -device support" section. It is recommended that you configure the -driver as module since it is currently the only way to pass parameters -to the driver or configure more than one bonding device. - - Build and install the new kernel and modules. - -1.2 Bonding Control Utility -------------------------------------- - - It is recommended to configure bonding via iproute2 (netlink) -or sysfs, the old ifenslave control utility is obsolete. - -2. Bonding Driver Options -========================= - - Options for the bonding driver are supplied as parameters to the -bonding module at load time, or are specified via sysfs. - - Module options may be given as command line arguments to the -insmod or modprobe command, but are usually specified in either the -/etc/modprobe.d/*.conf configuration files, or in a distro-specific -configuration file (some of which are detailed in the next section). - - Details on bonding support for sysfs is provided in the -"Configuring Bonding Manually via Sysfs" section, below. - - The available bonding driver parameters are listed below. If a -parameter is not specified the default value is used. When initially -configuring a bond, it is recommended "tail -f /var/log/messages" be -run in a separate window to watch for bonding driver error messages. - - It is critical that either the miimon or arp_interval and -arp_ip_target parameters be specified, otherwise serious network -degradation will occur during link failures. Very few devices do not -support at least miimon, so there is really no reason not to use it. - - Options with textual values will accept either the text name -or, for backwards compatibility, the option value. E.g., -"mode=802.3ad" and "mode=4" set the same mode. - - The parameters are as follows: - -active_slave - - Specifies the new active slave for modes that support it - (active-backup, balance-alb and balance-tlb). Possible values - are the name of any currently enslaved interface, or an empty - string. If a name is given, the slave and its link must be up in order - to be selected as the new active slave. If an empty string is - specified, the current active slave is cleared, and a new active - slave is selected automatically. - - Note that this is only available through the sysfs interface. No module - parameter by this name exists. - - The normal value of this option is the name of the currently - active slave, or the empty string if there is no active slave or - the current mode does not use an active slave. - -ad_actor_sys_prio - - In an AD system, this specifies the system priority. The allowed range - is 1 - 65535. If the value is not specified, it takes 65535 as the - default value. - - This parameter has effect only in 802.3ad mode and is available through - SysFs interface. - -ad_actor_system - - In an AD system, this specifies the mac-address for the actor in - protocol packet exchanges (LACPDUs). The value cannot be NULL or - multicast. It is preferred to have the local-admin bit set for this - mac but driver does not enforce it. If the value is not given then - system defaults to using the masters' mac address as actors' system - address. - - This parameter has effect only in 802.3ad mode and is available through - SysFs interface. - -ad_select - - Specifies the 802.3ad aggregation selection logic to use. The - possible values and their effects are: - - stable or 0 - - The active aggregator is chosen by largest aggregate - bandwidth. - - Reselection of the active aggregator occurs only when all - slaves of the active aggregator are down or the active - aggregator has no slaves. - - This is the default value. - - bandwidth or 1 - - The active aggregator is chosen by largest aggregate - bandwidth. Reselection occurs if: - - - A slave is added to or removed from the bond - - - Any slave's link state changes - - - Any slave's 802.3ad association state changes - - - The bond's administrative state changes to up - - count or 2 - - The active aggregator is chosen by the largest number of - ports (slaves). Reselection occurs as described under the - "bandwidth" setting, above. - - The bandwidth and count selection policies permit failover of - 802.3ad aggregations when partial failure of the active aggregator - occurs. This keeps the aggregator with the highest availability - (either in bandwidth or in number of ports) active at all times. - - This option was added in bonding version 3.4.0. - -ad_user_port_key - - In an AD system, the port-key has three parts as shown below - - - Bits Use - 00 Duplex - 01-05 Speed - 06-15 User-defined - - This defines the upper 10 bits of the port key. The values can be - from 0 - 1023. If not given, the system defaults to 0. - - This parameter has effect only in 802.3ad mode and is available through - SysFs interface. - -all_slaves_active - - Specifies that duplicate frames (received on inactive ports) should be - dropped (0) or delivered (1). - - Normally, bonding will drop duplicate frames (received on inactive - ports), which is desirable for most users. But there are some times - it is nice to allow duplicate frames to be delivered. - - The default value is 0 (drop duplicate frames received on inactive - ports). - -arp_interval - - Specifies the ARP link monitoring frequency in milliseconds. - - The ARP monitor works by periodically checking the slave - devices to determine whether they have sent or received - traffic recently (the precise criteria depends upon the - bonding mode, and the state of the slave). Regular traffic is - generated via ARP probes issued for the addresses specified by - the arp_ip_target option. - - This behavior can be modified by the arp_validate option, - below. - - If ARP monitoring is used in an etherchannel compatible mode - (modes 0 and 2), the switch should be configured in a mode - that evenly distributes packets across all links. If the - switch is configured to distribute the packets in an XOR - fashion, all replies from the ARP targets will be received on - the same link which could cause the other team members to - fail. ARP monitoring should not be used in conjunction with - miimon. A value of 0 disables ARP monitoring. The default - value is 0. - -arp_ip_target - - Specifies the IP addresses to use as ARP monitoring peers when - arp_interval is > 0. These are the targets of the ARP request - sent to determine the health of the link to the targets. - Specify these values in ddd.ddd.ddd.ddd format. Multiple IP - addresses must be separated by a comma. At least one IP - address must be given for ARP monitoring to function. The - maximum number of targets that can be specified is 16. The - default value is no IP addresses. - -arp_validate - - Specifies whether or not ARP probes and replies should be - validated in any mode that supports arp monitoring, or whether - non-ARP traffic should be filtered (disregarded) for link - monitoring purposes. - - Possible values are: - - none or 0 - - No validation or filtering is performed. - - active or 1 - - Validation is performed only for the active slave. - - backup or 2 - - Validation is performed only for backup slaves. - - all or 3 - - Validation is performed for all slaves. - - filter or 4 - - Filtering is applied to all slaves. No validation is - performed. - - filter_active or 5 - - Filtering is applied to all slaves, validation is performed - only for the active slave. - - filter_backup or 6 - - Filtering is applied to all slaves, validation is performed - only for backup slaves. - - Validation: - - Enabling validation causes the ARP monitor to examine the incoming - ARP requests and replies, and only consider a slave to be up if it - is receiving the appropriate ARP traffic. - - For an active slave, the validation checks ARP replies to confirm - that they were generated by an arp_ip_target. Since backup slaves - do not typically receive these replies, the validation performed - for backup slaves is on the broadcast ARP request sent out via the - active slave. It is possible that some switch or network - configurations may result in situations wherein the backup slaves - do not receive the ARP requests; in such a situation, validation - of backup slaves must be disabled. - - The validation of ARP requests on backup slaves is mainly helping - bonding to decide which slaves are more likely to work in case of - the active slave failure, it doesn't really guarantee that the - backup slave will work if it's selected as the next active slave. - - Validation is useful in network configurations in which multiple - bonding hosts are concurrently issuing ARPs to one or more targets - beyond a common switch. Should the link between the switch and - target fail (but not the switch itself), the probe traffic - generated by the multiple bonding instances will fool the standard - ARP monitor into considering the links as still up. Use of - validation can resolve this, as the ARP monitor will only consider - ARP requests and replies associated with its own instance of - bonding. - - Filtering: - - Enabling filtering causes the ARP monitor to only use incoming ARP - packets for link availability purposes. Arriving packets that are - not ARPs are delivered normally, but do not count when determining - if a slave is available. - - Filtering operates by only considering the reception of ARP - packets (any ARP packet, regardless of source or destination) when - determining if a slave has received traffic for link availability - purposes. - - Filtering is useful in network configurations in which significant - levels of third party broadcast traffic would fool the standard - ARP monitor into considering the links as still up. Use of - filtering can resolve this, as only ARP traffic is considered for - link availability purposes. - - This option was added in bonding version 3.1.0. - -arp_all_targets - - Specifies the quantity of arp_ip_targets that must be reachable - in order for the ARP monitor to consider a slave as being up. - This option affects only active-backup mode for slaves with - arp_validation enabled. - - Possible values are: - - any or 0 - - consider the slave up only when any of the arp_ip_targets - is reachable - - all or 1 - - consider the slave up only when all of the arp_ip_targets - are reachable - -downdelay - - Specifies the time, in milliseconds, to wait before disabling - a slave after a link failure has been detected. This option - is only valid for the miimon link monitor. The downdelay - value should be a multiple of the miimon value; if not, it - will be rounded down to the nearest multiple. The default - value is 0. - -fail_over_mac - - Specifies whether active-backup mode should set all slaves to - the same MAC address at enslavement (the traditional - behavior), or, when enabled, perform special handling of the - bond's MAC address in accordance with the selected policy. - - Possible values are: - - none or 0 - - This setting disables fail_over_mac, and causes - bonding to set all slaves of an active-backup bond to - the same MAC address at enslavement time. This is the - default. - - active or 1 - - The "active" fail_over_mac policy indicates that the - MAC address of the bond should always be the MAC - address of the currently active slave. The MAC - address of the slaves is not changed; instead, the MAC - address of the bond changes during a failover. - - This policy is useful for devices that cannot ever - alter their MAC address, or for devices that refuse - incoming broadcasts with their own source MAC (which - interferes with the ARP monitor). - - The down side of this policy is that every device on - the network must be updated via gratuitous ARP, - vs. just updating a switch or set of switches (which - often takes place for any traffic, not just ARP - traffic, if the switch snoops incoming traffic to - update its tables) for the traditional method. If the - gratuitous ARP is lost, communication may be - disrupted. - - When this policy is used in conjunction with the mii - monitor, devices which assert link up prior to being - able to actually transmit and receive are particularly - susceptible to loss of the gratuitous ARP, and an - appropriate updelay setting may be required. - - follow or 2 - - The "follow" fail_over_mac policy causes the MAC - address of the bond to be selected normally (normally - the MAC address of the first slave added to the bond). - However, the second and subsequent slaves are not set - to this MAC address while they are in a backup role; a - slave is programmed with the bond's MAC address at - failover time (and the formerly active slave receives - the newly active slave's MAC address). - - This policy is useful for multiport devices that - either become confused or incur a performance penalty - when multiple ports are programmed with the same MAC - address. - - - The default policy is none, unless the first slave cannot - change its MAC address, in which case the active policy is - selected by default. - - This option may be modified via sysfs only when no slaves are - present in the bond. - - This option was added in bonding version 3.2.0. The "follow" - policy was added in bonding version 3.3.0. - -lacp_rate - - Option specifying the rate in which we'll ask our link partner - to transmit LACPDU packets in 802.3ad mode. Possible values - are: - - slow or 0 - Request partner to transmit LACPDUs every 30 seconds - - fast or 1 - Request partner to transmit LACPDUs every 1 second - - The default is slow. - -max_bonds - - Specifies the number of bonding devices to create for this - instance of the bonding driver. E.g., if max_bonds is 3, and - the bonding driver is not already loaded, then bond0, bond1 - and bond2 will be created. The default value is 1. Specifying - a value of 0 will load bonding, but will not create any devices. - -miimon - - Specifies the MII link monitoring frequency in milliseconds. - This determines how often the link state of each slave is - inspected for link failures. A value of zero disables MII - link monitoring. A value of 100 is a good starting point. - The use_carrier option, below, affects how the link state is - determined. See the High Availability section for additional - information. The default value is 0. - -min_links - - Specifies the minimum number of links that must be active before - asserting carrier. It is similar to the Cisco EtherChannel min-links - feature. This allows setting the minimum number of member ports that - must be up (link-up state) before marking the bond device as up - (carrier on). This is useful for situations where higher level services - such as clustering want to ensure a minimum number of low bandwidth - links are active before switchover. This option only affect 802.3ad - mode. - - The default value is 0. This will cause carrier to be asserted (for - 802.3ad mode) whenever there is an active aggregator, regardless of the - number of available links in that aggregator. Note that, because an - aggregator cannot be active without at least one available link, - setting this option to 0 or to 1 has the exact same effect. - -mode - - Specifies one of the bonding policies. The default is - balance-rr (round robin). Possible values are: - - balance-rr or 0 - - Round-robin policy: Transmit packets in sequential - order from the first available slave through the - last. This mode provides load balancing and fault - tolerance. - - active-backup or 1 - - Active-backup policy: Only one slave in the bond is - active. A different slave becomes active if, and only - if, the active slave fails. The bond's MAC address is - externally visible on only one port (network adapter) - to avoid confusing the switch. - - In bonding version 2.6.2 or later, when a failover - occurs in active-backup mode, bonding will issue one - or more gratuitous ARPs on the newly active slave. - One gratuitous ARP is issued for the bonding master - interface and each VLAN interfaces configured above - it, provided that the interface has at least one IP - address configured. Gratuitous ARPs issued for VLAN - interfaces are tagged with the appropriate VLAN id. - - This mode provides fault tolerance. The primary - option, documented below, affects the behavior of this - mode. - - balance-xor or 2 - - XOR policy: Transmit based on the selected transmit - hash policy. The default policy is a simple [(source - MAC address XOR'd with destination MAC address XOR - packet type ID) modulo slave count]. Alternate transmit - policies may be selected via the xmit_hash_policy option, - described below. - - This mode provides load balancing and fault tolerance. - - broadcast or 3 - - Broadcast policy: transmits everything on all slave - interfaces. This mode provides fault tolerance. - - 802.3ad or 4 - - IEEE 802.3ad Dynamic link aggregation. Creates - aggregation groups that share the same speed and - duplex settings. Utilizes all slaves in the active - aggregator according to the 802.3ad specification. - - Slave selection for outgoing traffic is done according - to the transmit hash policy, which may be changed from - the default simple XOR policy via the xmit_hash_policy - option, documented below. Note that not all transmit - policies may be 802.3ad compliant, particularly in - regards to the packet mis-ordering requirements of - section 43.2.4 of the 802.3ad standard. Differing - peer implementations will have varying tolerances for - noncompliance. - - Prerequisites: - - 1. Ethtool support in the base drivers for retrieving - the speed and duplex of each slave. - - 2. A switch that supports IEEE 802.3ad Dynamic link - aggregation. - - Most switches will require some type of configuration - to enable 802.3ad mode. - - balance-tlb or 5 - - Adaptive transmit load balancing: channel bonding that - does not require any special switch support. - - In tlb_dynamic_lb=1 mode; the outgoing traffic is - distributed according to the current load (computed - relative to the speed) on each slave. - - In tlb_dynamic_lb=0 mode; the load balancing based on - current load is disabled and the load is distributed - only using the hash distribution. - - Incoming traffic is received by the current slave. - If the receiving slave fails, another slave takes over - the MAC address of the failed receiving slave. - - Prerequisite: - - Ethtool support in the base drivers for retrieving the - speed of each slave. - - balance-alb or 6 - - Adaptive load balancing: includes balance-tlb plus - receive load balancing (rlb) for IPV4 traffic, and - does not require any special switch support. The - receive load balancing is achieved by ARP negotiation. - The bonding driver intercepts the ARP Replies sent by - the local system on their way out and overwrites the - source hardware address with the unique hardware - address of one of the slaves in the bond such that - different peers use different hardware addresses for - the server. - - Receive traffic from connections created by the server - is also balanced. When the local system sends an ARP - Request the bonding driver copies and saves the peer's - IP information from the ARP packet. When the ARP - Reply arrives from the peer, its hardware address is - retrieved and the bonding driver initiates an ARP - reply to this peer assigning it to one of the slaves - in the bond. A problematic outcome of using ARP - negotiation for balancing is that each time that an - ARP request is broadcast it uses the hardware address - of the bond. Hence, peers learn the hardware address - of the bond and the balancing of receive traffic - collapses to the current slave. This is handled by - sending updates (ARP Replies) to all the peers with - their individually assigned hardware address such that - the traffic is redistributed. Receive traffic is also - redistributed when a new slave is added to the bond - and when an inactive slave is re-activated. The - receive load is distributed sequentially (round robin) - among the group of highest speed slaves in the bond. - - When a link is reconnected or a new slave joins the - bond the receive traffic is redistributed among all - active slaves in the bond by initiating ARP Replies - with the selected MAC address to each of the - clients. The updelay parameter (detailed below) must - be set to a value equal or greater than the switch's - forwarding delay so that the ARP Replies sent to the - peers will not be blocked by the switch. - - Prerequisites: - - 1. Ethtool support in the base drivers for retrieving - the speed of each slave. - - 2. Base driver support for setting the hardware - address of a device while it is open. This is - required so that there will always be one slave in the - team using the bond hardware address (the - curr_active_slave) while having a unique hardware - address for each slave in the bond. If the - curr_active_slave fails its hardware address is - swapped with the new curr_active_slave that was - chosen. - -num_grat_arp -num_unsol_na - - Specify the number of peer notifications (gratuitous ARPs and - unsolicited IPv6 Neighbor Advertisements) to be issued after a - failover event. As soon as the link is up on the new slave - (possibly immediately) a peer notification is sent on the - bonding device and each VLAN sub-device. This is repeated at - the rate specified by peer_notif_delay if the number is - greater than 1. - - The valid range is 0 - 255; the default value is 1. These options - affect only the active-backup mode. These options were added for - bonding versions 3.3.0 and 3.4.0 respectively. - - From Linux 3.0 and bonding version 3.7.1, these notifications - are generated by the ipv4 and ipv6 code and the numbers of - repetitions cannot be set independently. - -packets_per_slave - - Specify the number of packets to transmit through a slave before - moving to the next one. When set to 0 then a slave is chosen at - random. - - The valid range is 0 - 65535; the default value is 1. This option - has effect only in balance-rr mode. - -peer_notif_delay - - Specify the delay, in milliseconds, between each peer - notification (gratuitous ARP and unsolicited IPv6 Neighbor - Advertisement) when they are issued after a failover event. - This delay should be a multiple of the link monitor interval - (arp_interval or miimon, whichever is active). The default - value is 0 which means to match the value of the link monitor - interval. - -primary - - A string (eth0, eth2, etc) specifying which slave is the - primary device. The specified device will always be the - active slave while it is available. Only when the primary is - off-line will alternate devices be used. This is useful when - one slave is preferred over another, e.g., when one slave has - higher throughput than another. - - The primary option is only valid for active-backup(1), - balance-tlb (5) and balance-alb (6) mode. - -primary_reselect - - Specifies the reselection policy for the primary slave. This - affects how the primary slave is chosen to become the active slave - when failure of the active slave or recovery of the primary slave - occurs. This option is designed to prevent flip-flopping between - the primary slave and other slaves. Possible values are: - - always or 0 (default) - - The primary slave becomes the active slave whenever it - comes back up. - - better or 1 - - The primary slave becomes the active slave when it comes - back up, if the speed and duplex of the primary slave is - better than the speed and duplex of the current active - slave. - - failure or 2 - - The primary slave becomes the active slave only if the - current active slave fails and the primary slave is up. - - The primary_reselect setting is ignored in two cases: - - If no slaves are active, the first slave to recover is - made the active slave. - - When initially enslaved, the primary slave is always made - the active slave. - - Changing the primary_reselect policy via sysfs will cause an - immediate selection of the best active slave according to the new - policy. This may or may not result in a change of the active - slave, depending upon the circumstances. - - This option was added for bonding version 3.6.0. - -tlb_dynamic_lb - - Specifies if dynamic shuffling of flows is enabled in tlb - mode. The value has no effect on any other modes. - - The default behavior of tlb mode is to shuffle active flows across - slaves based on the load in that interval. This gives nice lb - characteristics but can cause packet reordering. If re-ordering is - a concern use this variable to disable flow shuffling and rely on - load balancing provided solely by the hash distribution. - xmit-hash-policy can be used to select the appropriate hashing for - the setup. - - The sysfs entry can be used to change the setting per bond device - and the initial value is derived from the module parameter. The - sysfs entry is allowed to be changed only if the bond device is - down. - - The default value is "1" that enables flow shuffling while value "0" - disables it. This option was added in bonding driver 3.7.1 - - -updelay - - Specifies the time, in milliseconds, to wait before enabling a - slave after a link recovery has been detected. This option is - only valid for the miimon link monitor. The updelay value - should be a multiple of the miimon value; if not, it will be - rounded down to the nearest multiple. The default value is 0. - -use_carrier - - Specifies whether or not miimon should use MII or ETHTOOL - ioctls vs. netif_carrier_ok() to determine the link - status. The MII or ETHTOOL ioctls are less efficient and - utilize a deprecated calling sequence within the kernel. The - netif_carrier_ok() relies on the device driver to maintain its - state with netif_carrier_on/off; at this writing, most, but - not all, device drivers support this facility. - - If bonding insists that the link is up when it should not be, - it may be that your network device driver does not support - netif_carrier_on/off. The default state for netif_carrier is - "carrier on," so if a driver does not support netif_carrier, - it will appear as if the link is always up. In this case, - setting use_carrier to 0 will cause bonding to revert to the - MII / ETHTOOL ioctl method to determine the link state. - - A value of 1 enables the use of netif_carrier_ok(), a value of - 0 will use the deprecated MII / ETHTOOL ioctls. The default - value is 1. - -xmit_hash_policy - - Selects the transmit hash policy to use for slave selection in - balance-xor, 802.3ad, and tlb modes. Possible values are: - - layer2 - - Uses XOR of hardware MAC addresses and packet type ID - field to generate the hash. The formula is - - hash = source MAC XOR destination MAC XOR packet type ID - slave number = hash modulo slave count - - This algorithm will place all traffic to a particular - network peer on the same slave. - - This algorithm is 802.3ad compliant. - - layer2+3 - - This policy uses a combination of layer2 and layer3 - protocol information to generate the hash. - - Uses XOR of hardware MAC addresses and IP addresses to - generate the hash. The formula is - - hash = source MAC XOR destination MAC XOR packet type ID - hash = hash XOR source IP XOR destination IP - hash = hash XOR (hash RSHIFT 16) - hash = hash XOR (hash RSHIFT 8) - And then hash is reduced modulo slave count. - - If the protocol is IPv6 then the source and destination - addresses are first hashed using ipv6_addr_hash. - - This algorithm will place all traffic to a particular - network peer on the same slave. For non-IP traffic, - the formula is the same as for the layer2 transmit - hash policy. - - This policy is intended to provide a more balanced - distribution of traffic than layer2 alone, especially - in environments where a layer3 gateway device is - required to reach most destinations. - - This algorithm is 802.3ad compliant. - - layer3+4 - - This policy uses upper layer protocol information, - when available, to generate the hash. This allows for - traffic to a particular network peer to span multiple - slaves, although a single connection will not span - multiple slaves. - - The formula for unfragmented TCP and UDP packets is - - hash = source port, destination port (as in the header) - hash = hash XOR source IP XOR destination IP - hash = hash XOR (hash RSHIFT 16) - hash = hash XOR (hash RSHIFT 8) - And then hash is reduced modulo slave count. - - If the protocol is IPv6 then the source and destination - addresses are first hashed using ipv6_addr_hash. - - For fragmented TCP or UDP packets and all other IPv4 and - IPv6 protocol traffic, the source and destination port - information is omitted. For non-IP traffic, the - formula is the same as for the layer2 transmit hash - policy. - - This algorithm is not fully 802.3ad compliant. A - single TCP or UDP conversation containing both - fragmented and unfragmented packets will see packets - striped across two interfaces. This may result in out - of order delivery. Most traffic types will not meet - this criteria, as TCP rarely fragments traffic, and - most UDP traffic is not involved in extended - conversations. Other implementations of 802.3ad may - or may not tolerate this noncompliance. - - encap2+3 - - This policy uses the same formula as layer2+3 but it - relies on skb_flow_dissect to obtain the header fields - which might result in the use of inner headers if an - encapsulation protocol is used. For example this will - improve the performance for tunnel users because the - packets will be distributed according to the encapsulated - flows. - - encap3+4 - - This policy uses the same formula as layer3+4 but it - relies on skb_flow_dissect to obtain the header fields - which might result in the use of inner headers if an - encapsulation protocol is used. For example this will - improve the performance for tunnel users because the - packets will be distributed according to the encapsulated - flows. - - The default value is layer2. This option was added in bonding - version 2.6.3. In earlier versions of bonding, this parameter - does not exist, and the layer2 policy is the only policy. The - layer2+3 value was added for bonding version 3.2.2. - -resend_igmp - - Specifies the number of IGMP membership reports to be issued after - a failover event. One membership report is issued immediately after - the failover, subsequent packets are sent in each 200ms interval. - - The valid range is 0 - 255; the default value is 1. A value of 0 - prevents the IGMP membership report from being issued in response - to the failover event. - - This option is useful for bonding modes balance-rr (0), active-backup - (1), balance-tlb (5) and balance-alb (6), in which a failover can - switch the IGMP traffic from one slave to another. Therefore a fresh - IGMP report must be issued to cause the switch to forward the incoming - IGMP traffic over the newly selected slave. - - This option was added for bonding version 3.7.0. - -lp_interval - - Specifies the number of seconds between instances where the bonding - driver sends learning packets to each slaves peer switch. - - The valid range is 1 - 0x7fffffff; the default value is 1. This Option - has effect only in balance-tlb and balance-alb modes. - -3. Configuring Bonding Devices -============================== - - You can configure bonding using either your distro's network -initialization scripts, or manually using either iproute2 or the -sysfs interface. Distros generally use one of three packages for the -network initialization scripts: initscripts, sysconfig or interfaces. -Recent versions of these packages have support for bonding, while older -versions do not. - - We will first describe the options for configuring bonding for -distros using versions of initscripts, sysconfig and interfaces with full -or partial support for bonding, then provide information on enabling -bonding without support from the network initialization scripts (i.e., -older versions of initscripts or sysconfig). - - If you're unsure whether your distro uses sysconfig, -initscripts or interfaces, or don't know if it's new enough, have no fear. -Determining this is fairly straightforward. - - First, look for a file called interfaces in /etc/network directory. -If this file is present in your system, then your system use interfaces. See -Configuration with Interfaces Support. - - Else, issue the command: - -$ rpm -qf /sbin/ifup - - It will respond with a line of text starting with either -"initscripts" or "sysconfig," followed by some numbers. This is the -package that provides your network initialization scripts. - - Next, to determine if your installation supports bonding, -issue the command: - -$ grep ifenslave /sbin/ifup - - If this returns any matches, then your initscripts or -sysconfig has support for bonding. - -3.1 Configuration with Sysconfig Support ----------------------------------------- - - This section applies to distros using a version of sysconfig -with bonding support, for example, SuSE Linux Enterprise Server 9. - - SuSE SLES 9's networking configuration system does support -bonding, however, at this writing, the YaST system configuration -front end does not provide any means to work with bonding devices. -Bonding devices can be managed by hand, however, as follows. - - First, if they have not already been configured, configure the -slave devices. On SLES 9, this is most easily done by running the -yast2 sysconfig configuration utility. The goal is for to create an -ifcfg-id file for each slave device. The simplest way to accomplish -this is to configure the devices for DHCP (this is only to get the -file ifcfg-id file created; see below for some issues with DHCP). The -name of the configuration file for each device will be of the form: - -ifcfg-id-xx:xx:xx:xx:xx:xx - - Where the "xx" portion will be replaced with the digits from -the device's permanent MAC address. - - Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been -created, it is necessary to edit the configuration files for the slave -devices (the MAC addresses correspond to those of the slave devices). -Before editing, the file will contain multiple lines, and will look -something like this: - -BOOTPROTO='dhcp' -STARTMODE='on' -USERCTL='no' -UNIQUE='XNzu.WeZGOGF+4wE' -_nm_name='bus-pci-0001:61:01.0' - - Change the BOOTPROTO and STARTMODE lines to the following: - -BOOTPROTO='none' -STARTMODE='off' - - Do not alter the UNIQUE or _nm_name lines. Remove any other -lines (USERCTL, etc). - - Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified, -it's time to create the configuration file for the bonding device -itself. This file is named ifcfg-bondX, where X is the number of the -bonding device to create, starting at 0. The first such file is -ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig -network configuration system will correctly start multiple instances -of bonding. - - The contents of the ifcfg-bondX file is as follows: - -BOOTPROTO="static" -BROADCAST="10.0.2.255" -IPADDR="10.0.2.10" -NETMASK="255.255.0.0" -NETWORK="10.0.2.0" -REMOTE_IPADDR="" -STARTMODE="onboot" -BONDING_MASTER="yes" -BONDING_MODULE_OPTS="mode=active-backup miimon=100" -BONDING_SLAVE0="eth0" -BONDING_SLAVE1="bus-pci-0000:06:08.1" - - Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK -values with the appropriate values for your network. - - The STARTMODE specifies when the device is brought online. -The possible values are: - - onboot: The device is started at boot time. If you're not - sure, this is probably what you want. - - manual: The device is started only when ifup is called - manually. Bonding devices may be configured this - way if you do not wish them to start automatically - at boot for some reason. - - hotplug: The device is started by a hotplug event. This is not - a valid choice for a bonding device. - - off or ignore: The device configuration is ignored. - - The line BONDING_MASTER='yes' indicates that the device is a -bonding master device. The only useful value is "yes." - - The contents of BONDING_MODULE_OPTS are supplied to the -instance of the bonding module for this device. Specify the options -for the bonding mode, link monitoring, and so on here. Do not include -the max_bonds bonding parameter; this will confuse the configuration -system if you have multiple bonding devices. - - Finally, supply one BONDING_SLAVEn="slave device" for each -slave. where "n" is an increasing value, one for each slave. The -"slave device" is either an interface name, e.g., "eth0", or a device -specifier for the network device. The interface name is easier to -find, but the ethN names are subject to change at boot time if, e.g., -a device early in the sequence has failed. The device specifiers -(bus-pci-0000:06:08.1 in the example above) specify the physical -network device, and will not change unless the device's bus location -changes (for example, it is moved from one PCI slot to another). The -example above uses one of each type for demonstration purposes; most -configurations will choose one or the other for all slave devices. - - When all configuration files have been modified or created, -networking must be restarted for the configuration changes to take -effect. This can be accomplished via the following: - -# /etc/init.d/network restart - - Note that the network control script (/sbin/ifdown) will -remove the bonding module as part of the network shutdown processing, -so it is not necessary to remove the module by hand if, e.g., the -module parameters have changed. - - Also, at this writing, YaST/YaST2 will not manage bonding -devices (they do not show bonding interfaces on its list of network -devices). It is necessary to edit the configuration file by hand to -change the bonding configuration. - - Additional general options and details of the ifcfg file -format can be found in an example ifcfg template file: - -/etc/sysconfig/network/ifcfg.template - - Note that the template does not document the various BONDING_ -settings described above, but does describe many of the other options. - -3.1.1 Using DHCP with Sysconfig -------------------------------- - - Under sysconfig, configuring a device with BOOTPROTO='dhcp' -will cause it to query DHCP for its IP address information. At this -writing, this does not function for bonding devices; the scripts -attempt to obtain the device address from DHCP prior to adding any of -the slave devices. Without active slaves, the DHCP requests are not -sent to the network. - -3.1.2 Configuring Multiple Bonds with Sysconfig ------------------------------------------------ - - The sysconfig network initialization system is capable of -handling multiple bonding devices. All that is necessary is for each -bonding instance to have an appropriately configured ifcfg-bondX file -(as described above). Do not specify the "max_bonds" parameter to any -instance of bonding, as this will confuse sysconfig. If you require -multiple bonding devices with identical parameters, create multiple -ifcfg-bondX files. - - Because the sysconfig scripts supply the bonding module -options in the ifcfg-bondX file, it is not necessary to add them to -the system /etc/modules.d/*.conf configuration files. - -3.2 Configuration with Initscripts Support ------------------------------------------- - - This section applies to distros using a recent version of -initscripts with bonding support, for example, Red Hat Enterprise Linux -version 3 or later, Fedora, etc. On these systems, the network -initialization scripts have knowledge of bonding, and can be configured to -control bonding devices. Note that older versions of the initscripts -package have lower levels of support for bonding; this will be noted where -applicable. - - These distros will not automatically load the network adapter -driver unless the ethX device is configured with an IP address. -Because of this constraint, users must manually configure a -network-script file for all physical adapters that will be members of -a bondX link. Network script files are located in the directory: - -/etc/sysconfig/network-scripts - - The file name must be prefixed with "ifcfg-eth" and suffixed -with the adapter's physical adapter number. For example, the script -for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0. -Place the following text in the file: - -DEVICE=eth0 -USERCTL=no -ONBOOT=yes -MASTER=bond0 -SLAVE=yes -BOOTPROTO=none - - The DEVICE= line will be different for every ethX device and -must correspond with the name of the file, i.e., ifcfg-eth1 must have -a device line of DEVICE=eth1. The setting of the MASTER= line will -also depend on the final bonding interface name chosen for your bond. -As with other network devices, these typically start at 0, and go up -one for each device, i.e., the first bonding instance is bond0, the -second is bond1, and so on. - - Next, create a bond network script. The file name for this -script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is -the number of the bond. For bond0 the file is named "ifcfg-bond0", -for bond1 it is named "ifcfg-bond1", and so on. Within that file, -place the following text: - -DEVICE=bond0 -IPADDR=192.168.1.1 -NETMASK=255.255.255.0 -NETWORK=192.168.1.0 -BROADCAST=192.168.1.255 -ONBOOT=yes -BOOTPROTO=none -USERCTL=no - - Be sure to change the networking specific lines (IPADDR, -NETMASK, NETWORK and BROADCAST) to match your network configuration. - - For later versions of initscripts, such as that found with Fedora -7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible, -and, indeed, preferable, to specify the bonding options in the ifcfg-bond0 -file, e.g. a line of the format: - -BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254" - - will configure the bond with the specified options. The options -specified in BONDING_OPTS are identical to the bonding module parameters -except for the arp_ip_target field when using versions of initscripts older -than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When -using older versions each target should be included as a separate option and -should be preceded by a '+' to indicate it should be added to the list of -queried targets, e.g., - - arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2 - - is the proper syntax to specify multiple targets. When specifying -options via BONDING_OPTS, it is not necessary to edit /etc/modprobe.d/*.conf. - - For even older versions of initscripts that do not support -BONDING_OPTS, it is necessary to edit /etc/modprobe.d/*.conf, depending upon -your distro) to load the bonding module with your desired options when the -bond0 interface is brought up. The following lines in /etc/modprobe.d/*.conf -will load the bonding module, and select its options: - -alias bond0 bonding -options bond0 mode=balance-alb miimon=100 - - Replace the sample parameters with the appropriate set of -options for your configuration. - - Finally run "/etc/rc.d/init.d/network restart" as root. This -will restart the networking subsystem and your bond link should be now -up and running. - -3.2.1 Using DHCP with Initscripts ---------------------------------- - - Recent versions of initscripts (the versions supplied with Fedora -Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to -work) have support for assigning IP information to bonding devices via -DHCP. - - To configure bonding for DHCP, configure it as described -above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp" -and add a line consisting of "TYPE=Bonding". Note that the TYPE value -is case sensitive. - -3.2.2 Configuring Multiple Bonds with Initscripts -------------------------------------------------- - - Initscripts packages that are included with Fedora 7 and Red Hat -Enterprise Linux 5 support multiple bonding interfaces by simply -specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the -number of the bond. This support requires sysfs support in the kernel, -and a bonding driver of version 3.0.0 or later. Other configurations may -not support this method for specifying multiple bonding interfaces; for -those instances, see the "Configuring Multiple Bonds Manually" section, -below. - -3.3 Configuring Bonding Manually with iproute2 ------------------------------------------------ - - This section applies to distros whose network initialization -scripts (the sysconfig or initscripts package) do not have specific -knowledge of bonding. One such distro is SuSE Linux Enterprise Server -version 8. - - The general method for these systems is to place the bonding -module parameters into a config file in /etc/modprobe.d/ (as -appropriate for the installed distro), then add modprobe and/or -`ip link` commands to the system's global init script. The name of -the global init script differs; for sysconfig, it is -/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local. - - For example, if you wanted to make a simple bond of two e100 -devices (presumed to be eth0 and eth1), and have it persist across -reboots, edit the appropriate file (/etc/init.d/boot.local or -/etc/rc.d/rc.local), and add the following: - -modprobe bonding mode=balance-alb miimon=100 -modprobe e100 -ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up -ip link set eth0 master bond0 -ip link set eth1 master bond0 - - Replace the example bonding module parameters and bond0 -network configuration (IP address, netmask, etc) with the appropriate -values for your configuration. - - Unfortunately, this method will not provide support for the -ifup and ifdown scripts on the bond devices. To reload the bonding -configuration, it is necessary to run the initialization script, e.g., - -# /etc/init.d/boot.local - - or - -# /etc/rc.d/rc.local - - It may be desirable in such a case to create a separate script -which only initializes the bonding configuration, then call that -separate script from within boot.local. This allows for bonding to be -enabled without re-running the entire global init script. - - To shut down the bonding devices, it is necessary to first -mark the bonding device itself as being down, then remove the -appropriate device driver modules. For our example above, you can do -the following: - -# ifconfig bond0 down -# rmmod bonding -# rmmod e100 - - Again, for convenience, it may be desirable to create a script -with these commands. - - -3.3.1 Configuring Multiple Bonds Manually ------------------------------------------ - - This section contains information on configuring multiple -bonding devices with differing options for those systems whose network -initialization scripts lack support for configuring multiple bonds. - - If you require multiple bonding devices, but all with the same -options, you may wish to use the "max_bonds" module parameter, -documented above. - - To create multiple bonding devices with differing options, it is -preferable to use bonding parameters exported by sysfs, documented in the -section below. - - For versions of bonding without sysfs support, the only means to -provide multiple instances of bonding with differing options is to load -the bonding driver multiple times. Note that current versions of the -sysconfig network initialization scripts handle this automatically; if -your distro uses these scripts, no special action is needed. See the -section Configuring Bonding Devices, above, if you're not sure about your -network initialization scripts. - - To load multiple instances of the module, it is necessary to -specify a different name for each instance (the module loading system -requires that every loaded module, even multiple instances of the same -module, have a unique name). This is accomplished by supplying multiple -sets of bonding options in /etc/modprobe.d/*.conf, for example: - -alias bond0 bonding -options bond0 -o bond0 mode=balance-rr miimon=100 - -alias bond1 bonding -options bond1 -o bond1 mode=balance-alb miimon=50 - - will load the bonding module two times. The first instance is -named "bond0" and creates the bond0 device in balance-rr mode with an -miimon of 100. The second instance is named "bond1" and creates the -bond1 device in balance-alb mode with an miimon of 50. - - In some circumstances (typically with older distributions), -the above does not work, and the second bonding instance never sees -its options. In that case, the second options line can be substituted -as follows: - -install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \ - mode=balance-alb miimon=50 - - This may be repeated any number of times, specifying a new and -unique name in place of bond1 for each subsequent instance. - - It has been observed that some Red Hat supplied kernels are unable -to rename modules at load time (the "-o bond1" part). Attempts to pass -that option to modprobe will produce an "Operation not permitted" error. -This has been reported on some Fedora Core kernels, and has been seen on -RHEL 4 as well. On kernels exhibiting this problem, it will be impossible -to configure multiple bonds with differing parameters (as they are older -kernels, and also lack sysfs support). - -3.4 Configuring Bonding Manually via Sysfs ------------------------------------------- - - Starting with version 3.0.0, Channel Bonding may be configured -via the sysfs interface. This interface allows dynamic configuration -of all bonds in the system without unloading the module. It also -allows for adding and removing bonds at runtime. Ifenslave is no -longer required, though it is still supported. - - Use of the sysfs interface allows you to use multiple bonds -with different configurations without having to reload the module. -It also allows you to use multiple, differently configured bonds when -bonding is compiled into the kernel. - - You must have the sysfs filesystem mounted to configure -bonding this way. The examples in this document assume that you -are using the standard mount point for sysfs, e.g. /sys. If your -sysfs filesystem is mounted elsewhere, you will need to adjust the -example paths accordingly. - -Creating and Destroying Bonds ------------------------------ -To add a new bond foo: -# echo +foo > /sys/class/net/bonding_masters - -To remove an existing bond bar: -# echo -bar > /sys/class/net/bonding_masters - -To show all existing bonds: -# cat /sys/class/net/bonding_masters - -NOTE: due to 4K size limitation of sysfs files, this list may be -truncated if you have more than a few hundred bonds. This is unlikely -to occur under normal operating conditions. - -Adding and Removing Slaves --------------------------- - Interfaces may be enslaved to a bond using the file -/sys/class/net/<bond>/bonding/slaves. The semantics for this file -are the same as for the bonding_masters file. - -To enslave interface eth0 to bond bond0: -# ifconfig bond0 up -# echo +eth0 > /sys/class/net/bond0/bonding/slaves - -To free slave eth0 from bond bond0: -# echo -eth0 > /sys/class/net/bond0/bonding/slaves - - When an interface is enslaved to a bond, symlinks between the -two are created in the sysfs filesystem. In this case, you would get -/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and -/sys/class/net/eth0/master pointing to /sys/class/net/bond0. - - This means that you can tell quickly whether or not an -interface is enslaved by looking for the master symlink. Thus: -# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves -will free eth0 from whatever bond it is enslaved to, regardless of -the name of the bond interface. - -Changing a Bond's Configuration -------------------------------- - Each bond may be configured individually by manipulating the -files located in /sys/class/net/<bond name>/bonding - - The names of these files correspond directly with the command- -line parameters described elsewhere in this file, and, with the -exception of arp_ip_target, they accept the same values. To see the -current setting, simply cat the appropriate file. - - A few examples will be given here; for specific usage -guidelines for each parameter, see the appropriate section in this -document. - -To configure bond0 for balance-alb mode: -# ifconfig bond0 down -# echo 6 > /sys/class/net/bond0/bonding/mode - - or - -# echo balance-alb > /sys/class/net/bond0/bonding/mode - NOTE: The bond interface must be down before the mode can be -changed. - -To enable MII monitoring on bond0 with a 1 second interval: -# echo 1000 > /sys/class/net/bond0/bonding/miimon - NOTE: If ARP monitoring is enabled, it will disabled when MII -monitoring is enabled, and vice-versa. - -To add ARP targets: -# echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target -# echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target - NOTE: up to 16 target addresses may be specified. - -To remove an ARP target: -# echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target - -To configure the interval between learning packet transmits: -# echo 12 > /sys/class/net/bond0/bonding/lp_interval - NOTE: the lp_interval is the number of seconds between instances where -the bonding driver sends learning packets to each slaves peer switch. The -default interval is 1 second. - -Example Configuration ---------------------- - We begin with the same example that is shown in section 3.3, -executed with sysfs, and without using ifenslave. - - To make a simple bond of two e100 devices (presumed to be eth0 -and eth1), and have it persist across reboots, edit the appropriate -file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the -following: - -modprobe bonding -modprobe e100 -echo balance-alb > /sys/class/net/bond0/bonding/mode -ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up -echo 100 > /sys/class/net/bond0/bonding/miimon -echo +eth0 > /sys/class/net/bond0/bonding/slaves -echo +eth1 > /sys/class/net/bond0/bonding/slaves - - To add a second bond, with two e1000 interfaces in -active-backup mode, using ARP monitoring, add the following lines to -your init script: - -modprobe e1000 -echo +bond1 > /sys/class/net/bonding_masters -echo active-backup > /sys/class/net/bond1/bonding/mode -ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up -echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target -echo 2000 > /sys/class/net/bond1/bonding/arp_interval -echo +eth2 > /sys/class/net/bond1/bonding/slaves -echo +eth3 > /sys/class/net/bond1/bonding/slaves - -3.5 Configuration with Interfaces Support ------------------------------------------ - - This section applies to distros which use /etc/network/interfaces file -to describe network interface configuration, most notably Debian and it's -derivatives. - - The ifup and ifdown commands on Debian don't support bonding out of -the box. The ifenslave-2.6 package should be installed to provide bonding -support. Once installed, this package will provide bond-* options to be used -into /etc/network/interfaces. - - Note that ifenslave-2.6 package will load the bonding module and use -the ifenslave command when appropriate. - -Example Configurations ----------------------- - -In /etc/network/interfaces, the following stanza will configure bond0, in -active-backup mode, with eth0 and eth1 as slaves. - -auto bond0 -iface bond0 inet dhcp - bond-slaves eth0 eth1 - bond-mode active-backup - bond-miimon 100 - bond-primary eth0 eth1 - -If the above configuration doesn't work, you might have a system using -upstart for system startup. This is most notably true for recent -Ubuntu versions. The following stanza in /etc/network/interfaces will -produce the same result on those systems. - -auto bond0 -iface bond0 inet dhcp - bond-slaves none - bond-mode active-backup - bond-miimon 100 - -auto eth0 -iface eth0 inet manual - bond-master bond0 - bond-primary eth0 eth1 - -auto eth1 -iface eth1 inet manual - bond-master bond0 - bond-primary eth0 eth1 - -For a full list of bond-* supported options in /etc/network/interfaces and some -more advanced examples tailored to you particular distros, see the files in -/usr/share/doc/ifenslave-2.6. - -3.6 Overriding Configuration for Special Cases ----------------------------------------------- - -When using the bonding driver, the physical port which transmits a frame is -typically selected by the bonding driver, and is not relevant to the user or -system administrator. The output port is simply selected using the policies of -the selected bonding mode. On occasion however, it is helpful to direct certain -classes of traffic to certain physical interfaces on output to implement -slightly more complex policies. For example, to reach a web server over a -bonded interface in which eth0 connects to a private network, while eth1 -connects via a public network, it may be desirous to bias the bond to send said -traffic over eth0 first, using eth1 only as a fall back, while all other traffic -can safely be sent over either interface. Such configurations may be achieved -using the traffic control utilities inherent in linux. - -By default the bonding driver is multiqueue aware and 16 queues are created -when the driver initializes (see Documentation/networking/multiqueue.txt -for details). If more or less queues are desired the module parameter -tx_queues can be used to change this value. There is no sysfs parameter -available as the allocation is done at module init time. - -The output of the file /proc/net/bonding/bondX has changed so the output Queue -ID is now printed for each slave: - -Bonding Mode: fault-tolerance (active-backup) -Primary Slave: None -Currently Active Slave: eth0 -MII Status: up -MII Polling Interval (ms): 0 -Up Delay (ms): 0 -Down Delay (ms): 0 - -Slave Interface: eth0 -MII Status: up -Link Failure Count: 0 -Permanent HW addr: 00:1a:a0:12:8f:cb -Slave queue ID: 0 - -Slave Interface: eth1 -MII Status: up -Link Failure Count: 0 -Permanent HW addr: 00:1a:a0:12:8f:cc -Slave queue ID: 2 - -The queue_id for a slave can be set using the command: - -# echo "eth1:2" > /sys/class/net/bond0/bonding/queue_id - -Any interface that needs a queue_id set should set it with multiple calls -like the one above until proper priorities are set for all interfaces. On -distributions that allow configuration via initscripts, multiple 'queue_id' -arguments can be added to BONDING_OPTS to set all needed slave queues. - -These queue id's can be used in conjunction with the tc utility to configure -a multiqueue qdisc and filters to bias certain traffic to transmit on certain -slave devices. For instance, say we wanted, in the above configuration to -force all traffic bound to 192.168.1.100 to use eth1 in the bond as its output -device. The following commands would accomplish this: - -# tc qdisc add dev bond0 handle 1 root multiq - -# tc filter add dev bond0 protocol ip parent 1: prio 1 u32 match ip dst \ - 192.168.1.100 action skbedit queue_mapping 2 - -These commands tell the kernel to attach a multiqueue queue discipline to the -bond0 interface and filter traffic enqueued to it, such that packets with a dst -ip of 192.168.1.100 have their output queue mapping value overwritten to 2. -This value is then passed into the driver, causing the normal output path -selection policy to be overridden, selecting instead qid 2, which maps to eth1. - -Note that qid values begin at 1. Qid 0 is reserved to initiate to the driver -that normal output policy selection should take place. One benefit to simply -leaving the qid for a slave to 0 is the multiqueue awareness in the bonding -driver that is now present. This awareness allows tc filters to be placed on -slave devices as well as bond devices and the bonding driver will simply act as -a pass-through for selecting output queues on the slave device rather than -output port selection. - -This feature first appeared in bonding driver version 3.7.0 and support for -output slave selection was limited to round-robin and active-backup modes. - -3.7 Configuring LACP for 802.3ad mode in a more secure way ----------------------------------------------------------- - -When using 802.3ad bonding mode, the Actor (host) and Partner (switch) -exchange LACPDUs. These LACPDUs cannot be sniffed, because they are -destined to link local mac addresses (which switches/bridges are not -supposed to forward). However, most of the values are easily predictable -or are simply the machine's MAC address (which is trivially known to all -other hosts in the same L2). This implies that other machines in the L2 -domain can spoof LACPDU packets from other hosts to the switch and potentially -cause mayhem by joining (from the point of view of the switch) another -machine's aggregate, thus receiving a portion of that hosts incoming -traffic and / or spoofing traffic from that machine themselves (potentially -even successfully terminating some portion of flows). Though this is not -a likely scenario, one could avoid this possibility by simply configuring -few bonding parameters: - - (a) ad_actor_system : You can set a random mac-address that can be used for - these LACPDU exchanges. The value can not be either NULL or Multicast. - Also it's preferable to set the local-admin bit. Following shell code - generates a random mac-address as described above. - - # sys_mac_addr=$(printf '%02x:%02x:%02x:%02x:%02x:%02x' \ - $(( (RANDOM & 0xFE) | 0x02 )) \ - $(( RANDOM & 0xFF )) \ - $(( RANDOM & 0xFF )) \ - $(( RANDOM & 0xFF )) \ - $(( RANDOM & 0xFF )) \ - $(( RANDOM & 0xFF ))) - # echo $sys_mac_addr > /sys/class/net/bond0/bonding/ad_actor_system - - (b) ad_actor_sys_prio : Randomize the system priority. The default value - is 65535, but system can take the value from 1 - 65535. Following shell - code generates random priority and sets it. - - # sys_prio=$(( 1 + RANDOM + RANDOM )) - # echo $sys_prio > /sys/class/net/bond0/bonding/ad_actor_sys_prio - - (c) ad_user_port_key : Use the user portion of the port-key. The default - keeps this empty. These are the upper 10 bits of the port-key and value - ranges from 0 - 1023. Following shell code generates these 10 bits and - sets it. - - # usr_port_key=$(( RANDOM & 0x3FF )) - # echo $usr_port_key > /sys/class/net/bond0/bonding/ad_user_port_key - - -4 Querying Bonding Configuration -================================= - -4.1 Bonding Configuration -------------------------- - - Each bonding device has a read-only file residing in the -/proc/net/bonding directory. The file contents include information -about the bonding configuration, options and state of each slave. - - For example, the contents of /proc/net/bonding/bond0 after the -driver is loaded with parameters of mode=0 and miimon=1000 is -generally as follows: - - Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004) - Bonding Mode: load balancing (round-robin) - Currently Active Slave: eth0 - MII Status: up - MII Polling Interval (ms): 1000 - Up Delay (ms): 0 - Down Delay (ms): 0 - - Slave Interface: eth1 - MII Status: up - Link Failure Count: 1 - - Slave Interface: eth0 - MII Status: up - Link Failure Count: 1 - - The precise format and contents will change depending upon the -bonding configuration, state, and version of the bonding driver. - -4.2 Network configuration -------------------------- - - The network configuration can be inspected using the ifconfig -command. Bonding devices will have the MASTER flag set; Bonding slave -devices will have the SLAVE flag set. The ifconfig output does not -contain information on which slaves are associated with which masters. - - In the example below, the bond0 interface is the master -(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of -bond0 have the same MAC address (HWaddr) as bond0 for all modes except -TLB and ALB that require a unique MAC address for each slave. - -# /sbin/ifconfig -bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 - inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0 - UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 - RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0 - TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0 - collisions:0 txqueuelen:0 - -eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 - UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 - RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0 - TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0 - collisions:0 txqueuelen:100 - Interrupt:10 Base address:0x1080 - -eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4 - UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1 - RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0 - TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0 - collisions:0 txqueuelen:100 - Interrupt:9 Base address:0x1400 - -5. Switch Configuration -======================= - - For this section, "switch" refers to whatever system the -bonded devices are directly connected to (i.e., where the other end of -the cable plugs into). This may be an actual dedicated switch device, -or it may be another regular system (e.g., another computer running -Linux), - - The active-backup, balance-tlb and balance-alb modes do not -require any specific configuration of the switch. - - The 802.3ad mode requires that the switch have the appropriate -ports configured as an 802.3ad aggregation. The precise method used -to configure this varies from switch to switch, but, for example, a -Cisco 3550 series switch requires that the appropriate ports first be -grouped together in a single etherchannel instance, then that -etherchannel is set to mode "lacp" to enable 802.3ad (instead of -standard EtherChannel). - - The balance-rr, balance-xor and broadcast modes generally -require that the switch have the appropriate ports grouped together. -The nomenclature for such a group differs between switches, it may be -called an "etherchannel" (as in the Cisco example, above), a "trunk -group" or some other similar variation. For these modes, each switch -will also have its own configuration options for the switch's transmit -policy to the bond. Typical choices include XOR of either the MAC or -IP addresses. The transmit policy of the two peers does not need to -match. For these three modes, the bonding mode really selects a -transmit policy for an EtherChannel group; all three will interoperate -with another EtherChannel group. - - -6. 802.1q VLAN Support -====================== - - It is possible to configure VLAN devices over a bond interface -using the 8021q driver. However, only packets coming from the 8021q -driver and passing through bonding will be tagged by default. Self -generated packets, for example, bonding's learning packets or ARP -packets generated by either ALB mode or the ARP monitor mechanism, are -tagged internally by bonding itself. As a result, bonding must -"learn" the VLAN IDs configured above it, and use those IDs to tag -self generated packets. - - For reasons of simplicity, and to support the use of adapters -that can do VLAN hardware acceleration offloading, the bonding -interface declares itself as fully hardware offloading capable, it gets -the add_vid/kill_vid notifications to gather the necessary -information, and it propagates those actions to the slaves. In case -of mixed adapter types, hardware accelerated tagged packets that -should go through an adapter that is not offloading capable are -"un-accelerated" by the bonding driver so the VLAN tag sits in the -regular location. - - VLAN interfaces *must* be added on top of a bonding interface -only after enslaving at least one slave. The bonding interface has a -hardware address of 00:00:00:00:00:00 until the first slave is added. -If the VLAN interface is created prior to the first enslavement, it -would pick up the all-zeroes hardware address. Once the first slave -is attached to the bond, the bond device itself will pick up the -slave's hardware address, which is then available for the VLAN device. - - Also, be aware that a similar problem can occur if all slaves -are released from a bond that still has one or more VLAN interfaces on -top of it. When a new slave is added, the bonding interface will -obtain its hardware address from the first slave, which might not -match the hardware address of the VLAN interfaces (which was -ultimately copied from an earlier slave). - - There are two methods to insure that the VLAN device operates -with the correct hardware address if all slaves are removed from a -bond interface: - - 1. Remove all VLAN interfaces then recreate them - - 2. Set the bonding interface's hardware address so that it -matches the hardware address of the VLAN interfaces. - - Note that changing a VLAN interface's HW address would set the -underlying device -- i.e. the bonding interface -- to promiscuous -mode, which might not be what you want. - - -7. Link Monitoring -================== - - The bonding driver at present supports two schemes for -monitoring a slave device's link state: the ARP monitor and the MII -monitor. - - At the present time, due to implementation restrictions in the -bonding driver itself, it is not possible to enable both ARP and MII -monitoring simultaneously. - -7.1 ARP Monitor Operation -------------------------- - - The ARP monitor operates as its name suggests: it sends ARP -queries to one or more designated peer systems on the network, and -uses the response as an indication that the link is operating. This -gives some assurance that traffic is actually flowing to and from one -or more peers on the local network. - - The ARP monitor relies on the device driver itself to verify -that traffic is flowing. In particular, the driver must keep up to -date the last receive time, dev->last_rx. Drivers that use NETIF_F_LLTX -flag must also update netdev_queue->trans_start. If they do not, then the -ARP monitor will immediately fail any slaves using that driver, and -those slaves will stay down. If networking monitoring (tcpdump, etc) -shows the ARP requests and replies on the network, then it may be that -your device driver is not updating last_rx and trans_start. - -7.2 Configuring Multiple ARP Targets ------------------------------------- - - While ARP monitoring can be done with just one target, it can -be useful in a High Availability setup to have several targets to -monitor. In the case of just one target, the target itself may go -down or have a problem making it unresponsive to ARP requests. Having -an additional target (or several) increases the reliability of the ARP -monitoring. - - Multiple ARP targets must be separated by commas as follows: - -# example options for ARP monitoring with three targets -alias bond0 bonding -options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9 - - For just a single target the options would resemble: - -# example options for ARP monitoring with one target -alias bond0 bonding -options bond0 arp_interval=60 arp_ip_target=192.168.0.100 - - -7.3 MII Monitor Operation -------------------------- - - The MII monitor monitors only the carrier state of the local -network interface. It accomplishes this in one of three ways: by -depending upon the device driver to maintain its carrier state, by -querying the device's MII registers, or by making an ethtool query to -the device. - - If the use_carrier module parameter is 1 (the default value), -then the MII monitor will rely on the driver for carrier state -information (via the netif_carrier subsystem). As explained in the -use_carrier parameter information, above, if the MII monitor fails to -detect carrier loss on the device (e.g., when the cable is physically -disconnected), it may be that the driver does not support -netif_carrier. - - If use_carrier is 0, then the MII monitor will first query the -device's (via ioctl) MII registers and check the link state. If that -request fails (not just that it returns carrier down), then the MII -monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain -the same information. If both methods fail (i.e., the driver either -does not support or had some error in processing both the MII register -and ethtool requests), then the MII monitor will assume the link is -up. - -8. Potential Sources of Trouble -=============================== - -8.1 Adventures in Routing -------------------------- - - When bonding is configured, it is important that the slave -devices not have routes that supersede routes of the master (or, -generally, not have routes at all). For example, suppose the bonding -device bond0 has two slaves, eth0 and eth1, and the routing table is -as follows: - -Kernel IP routing table -Destination Gateway Genmask Flags MSS Window irtt Iface -10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0 -10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1 -10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0 -127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo - - This routing configuration will likely still update the -receive/transmit times in the driver (needed by the ARP monitor), but -may bypass the bonding driver (because outgoing traffic to, in this -case, another host on network 10 would use eth0 or eth1 before bond0). - - The ARP monitor (and ARP itself) may become confused by this -configuration, because ARP requests (generated by the ARP monitor) -will be sent on one interface (bond0), but the corresponding reply -will arrive on a different interface (eth0). This reply looks to ARP -as an unsolicited ARP reply (because ARP matches replies on an -interface basis), and is discarded. The MII monitor is not affected -by the state of the routing table. - - The solution here is simply to insure that slaves do not have -routes of their own, and if for some reason they must, those routes do -not supersede routes of their master. This should generally be the -case, but unusual configurations or errant manual or automatic static -route additions may cause trouble. - -8.2 Ethernet Device Renaming ----------------------------- - - On systems with network configuration scripts that do not -associate physical devices directly with network interface names (so -that the same physical device always has the same "ethX" name), it may -be necessary to add some special logic to config files in -/etc/modprobe.d/. - - For example, given a modules.conf containing the following: - -alias bond0 bonding -options bond0 mode=some-mode miimon=50 -alias eth0 tg3 -alias eth1 tg3 -alias eth2 e1000 -alias eth3 e1000 - - If neither eth0 and eth1 are slaves to bond0, then when the -bond0 interface comes up, the devices may end up reordered. This -happens because bonding is loaded first, then its slave device's -drivers are loaded next. Since no other drivers have been loaded, -when the e1000 driver loads, it will receive eth0 and eth1 for its -devices, but the bonding configuration tries to enslave eth2 and eth3 -(which may later be assigned to the tg3 devices). - - Adding the following: - -add above bonding e1000 tg3 - - causes modprobe to load e1000 then tg3, in that order, when -bonding is loaded. This command is fully documented in the -modules.conf manual page. - - On systems utilizing modprobe an equivalent problem can occur. -In this case, the following can be added to config files in -/etc/modprobe.d/ as: - -softdep bonding pre: tg3 e1000 - - This will load tg3 and e1000 modules before loading the bonding one. -Full documentation on this can be found in the modprobe.d and modprobe -manual pages. - -8.3. Painfully Slow Or No Failed Link Detection By Miimon ---------------------------------------------------------- - - By default, bonding enables the use_carrier option, which -instructs bonding to trust the driver to maintain carrier state. - - As discussed in the options section, above, some drivers do -not support the netif_carrier_on/_off link state tracking system. -With use_carrier enabled, bonding will always see these links as up, -regardless of their actual state. - - Additionally, other drivers do support netif_carrier, but do -not maintain it in real time, e.g., only polling the link state at -some fixed interval. In this case, miimon will detect failures, but -only after some long period of time has expired. If it appears that -miimon is very slow in detecting link failures, try specifying -use_carrier=0 to see if that improves the failure detection time. If -it does, then it may be that the driver checks the carrier state at a -fixed interval, but does not cache the MII register values (so the -use_carrier=0 method of querying the registers directly works). If -use_carrier=0 does not improve the failover, then the driver may cache -the registers, or the problem may be elsewhere. - - Also, remember that miimon only checks for the device's -carrier state. It has no way to determine the state of devices on or -beyond other ports of a switch, or if a switch is refusing to pass -traffic while still maintaining carrier on. - -9. SNMP agents -=============== - - If running SNMP agents, the bonding driver should be loaded -before any network drivers participating in a bond. This requirement -is due to the interface index (ipAdEntIfIndex) being associated to -the first interface found with a given IP address. That is, there is -only one ipAdEntIfIndex for each IP address. For example, if eth0 and -eth1 are slaves of bond0 and the driver for eth0 is loaded before the -bonding driver, the interface for the IP address will be associated -with the eth0 interface. This configuration is shown below, the IP -address 192.168.1.1 has an interface index of 2 which indexes to eth0 -in the ifDescr table (ifDescr.2). - - interfaces.ifTable.ifEntry.ifDescr.1 = lo - interfaces.ifTable.ifEntry.ifDescr.2 = eth0 - interfaces.ifTable.ifEntry.ifDescr.3 = eth1 - interfaces.ifTable.ifEntry.ifDescr.4 = eth2 - interfaces.ifTable.ifEntry.ifDescr.5 = eth3 - interfaces.ifTable.ifEntry.ifDescr.6 = bond0 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 - - This problem is avoided by loading the bonding driver before -any network drivers participating in a bond. Below is an example of -loading the bonding driver first, the IP address 192.168.1.1 is -correctly associated with ifDescr.2. - - interfaces.ifTable.ifEntry.ifDescr.1 = lo - interfaces.ifTable.ifEntry.ifDescr.2 = bond0 - interfaces.ifTable.ifEntry.ifDescr.3 = eth0 - interfaces.ifTable.ifEntry.ifDescr.4 = eth1 - interfaces.ifTable.ifEntry.ifDescr.5 = eth2 - interfaces.ifTable.ifEntry.ifDescr.6 = eth3 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5 - ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 - - While some distributions may not report the interface name in -ifDescr, the association between the IP address and IfIndex remains -and SNMP functions such as Interface_Scan_Next will report that -association. - -10. Promiscuous mode -==================== - - When running network monitoring tools, e.g., tcpdump, it is -common to enable promiscuous mode on the device, so that all traffic -is seen (instead of seeing only traffic destined for the local host). -The bonding driver handles promiscuous mode changes to the bonding -master device (e.g., bond0), and propagates the setting to the slave -devices. - - For the balance-rr, balance-xor, broadcast, and 802.3ad modes, -the promiscuous mode setting is propagated to all slaves. - - For the active-backup, balance-tlb and balance-alb modes, the -promiscuous mode setting is propagated only to the active slave. - - For balance-tlb mode, the active slave is the slave currently -receiving inbound traffic. - - For balance-alb mode, the active slave is the slave used as a -"primary." This slave is used for mode-specific control traffic, for -sending to peers that are unassigned or if the load is unbalanced. - - For the active-backup, balance-tlb and balance-alb modes, when -the active slave changes (e.g., due to a link failure), the -promiscuous setting will be propagated to the new active slave. - -11. Configuring Bonding for High Availability -============================================= - - High Availability refers to configurations that provide -maximum network availability by having redundant or backup devices, -links or switches between the host and the rest of the world. The -goal is to provide the maximum availability of network connectivity -(i.e., the network always works), even though other configurations -could provide higher throughput. - -11.1 High Availability in a Single Switch Topology --------------------------------------------------- - - If two hosts (or a host and a single switch) are directly -connected via multiple physical links, then there is no availability -penalty to optimizing for maximum bandwidth. In this case, there is -only one switch (or peer), so if it fails, there is no alternative -access to fail over to. Additionally, the bonding load balance modes -support link monitoring of their members, so if individual links fail, -the load will be rebalanced across the remaining devices. - - See Section 12, "Configuring Bonding for Maximum Throughput" -for information on configuring bonding with one peer device. - -11.2 High Availability in a Multiple Switch Topology ----------------------------------------------------- - - With multiple switches, the configuration of bonding and the -network changes dramatically. In multiple switch topologies, there is -a trade off between network availability and usable bandwidth. - - Below is a sample network, configured to maximize the -availability of the network: - - | | - |port3 port3| - +-----+----+ +-----+----+ - | |port2 ISL port2| | - | switch A +--------------------------+ switch B | - | | | | - +-----+----+ +-----++---+ - |port1 port1| - | +-------+ | - +-------------+ host1 +---------------+ - eth0 +-------+ eth1 - - In this configuration, there is a link between the two -switches (ISL, or inter switch link), and multiple ports connecting to -the outside world ("port3" on each switch). There is no technical -reason that this could not be extended to a third switch. - -11.2.1 HA Bonding Mode Selection for Multiple Switch Topology -------------------------------------------------------------- - - In a topology such as the example above, the active-backup and -broadcast modes are the only useful bonding modes when optimizing for -availability; the other modes require all links to terminate on the -same peer for them to behave rationally. - -active-backup: This is generally the preferred mode, particularly if - the switches have an ISL and play together well. If the - network configuration is such that one switch is specifically - a backup switch (e.g., has lower capacity, higher cost, etc), - then the primary option can be used to insure that the - preferred link is always used when it is available. - -broadcast: This mode is really a special purpose mode, and is suitable - only for very specific needs. For example, if the two - switches are not connected (no ISL), and the networks beyond - them are totally independent. In this case, if it is - necessary for some specific one-way traffic to reach both - independent networks, then the broadcast mode may be suitable. - -11.2.2 HA Link Monitoring Selection for Multiple Switch Topology ----------------------------------------------------------------- - - The choice of link monitoring ultimately depends upon your -switch. If the switch can reliably fail ports in response to other -failures, then either the MII or ARP monitors should work. For -example, in the above example, if the "port3" link fails at the remote -end, the MII monitor has no direct means to detect this. The ARP -monitor could be configured with a target at the remote end of port3, -thus detecting that failure without switch support. - - In general, however, in a multiple switch topology, the ARP -monitor can provide a higher level of reliability in detecting end to -end connectivity failures (which may be caused by the failure of any -individual component to pass traffic for any reason). Additionally, -the ARP monitor should be configured with multiple targets (at least -one for each switch in the network). This will insure that, -regardless of which switch is active, the ARP monitor has a suitable -target to query. - - Note, also, that of late many switches now support a functionality -generally referred to as "trunk failover." This is a feature of the -switch that causes the link state of a particular switch port to be set -down (or up) when the state of another switch port goes down (or up). -Its purpose is to propagate link failures from logically "exterior" ports -to the logically "interior" ports that bonding is able to monitor via -miimon. Availability and configuration for trunk failover varies by -switch, but this can be a viable alternative to the ARP monitor when using -suitable switches. - -12. Configuring Bonding for Maximum Throughput -============================================== - -12.1 Maximizing Throughput in a Single Switch Topology ------------------------------------------------------- - - In a single switch configuration, the best method to maximize -throughput depends upon the application and network environment. The -various load balancing modes each have strengths and weaknesses in -different environments, as detailed below. - - For this discussion, we will break down the topologies into -two categories. Depending upon the destination of most traffic, we -categorize them into either "gatewayed" or "local" configurations. - - In a gatewayed configuration, the "switch" is acting primarily -as a router, and the majority of traffic passes through this router to -other networks. An example would be the following: - - - +----------+ +----------+ - | |eth0 port1| | to other networks - | Host A +---------------------+ router +-------------------> - | +---------------------+ | Hosts B and C are out - | |eth1 port2| | here somewhere - +----------+ +----------+ - - The router may be a dedicated router device, or another host -acting as a gateway. For our discussion, the important point is that -the majority of traffic from Host A will pass through the router to -some other network before reaching its final destination. - - In a gatewayed network configuration, although Host A may -communicate with many other systems, all of its traffic will be sent -and received via one other peer on the local network, the router. - - Note that the case of two systems connected directly via -multiple physical links is, for purposes of configuring bonding, the -same as a gatewayed configuration. In that case, it happens that all -traffic is destined for the "gateway" itself, not some other network -beyond the gateway. - - In a local configuration, the "switch" is acting primarily as -a switch, and the majority of traffic passes through this switch to -reach other stations on the same network. An example would be the -following: - - +----------+ +----------+ +--------+ - | |eth0 port1| +-------+ Host B | - | Host A +------------+ switch |port3 +--------+ - | +------------+ | +--------+ - | |eth1 port2| +------------------+ Host C | - +----------+ +----------+port4 +--------+ - - - Again, the switch may be a dedicated switch device, or another -host acting as a gateway. For our discussion, the important point is -that the majority of traffic from Host A is destined for other hosts -on the same local network (Hosts B and C in the above example). - - In summary, in a gatewayed configuration, traffic to and from -the bonded device will be to the same MAC level peer on the network -(the gateway itself, i.e., the router), regardless of its final -destination. In a local configuration, traffic flows directly to and -from the final destinations, thus, each destination (Host B, Host C) -will be addressed directly by their individual MAC addresses. - - This distinction between a gatewayed and a local network -configuration is important because many of the load balancing modes -available use the MAC addresses of the local network source and -destination to make load balancing decisions. The behavior of each -mode is described below. - - -12.1.1 MT Bonding Mode Selection for Single Switch Topology ------------------------------------------------------------ - - This configuration is the easiest to set up and to understand, -although you will have to decide which bonding mode best suits your -needs. The trade offs for each mode are detailed below: - -balance-rr: This mode is the only mode that will permit a single - TCP/IP connection to stripe traffic across multiple - interfaces. It is therefore the only mode that will allow a - single TCP/IP stream to utilize more than one interface's - worth of throughput. This comes at a cost, however: the - striping generally results in peer systems receiving packets out - of order, causing TCP/IP's congestion control system to kick - in, often by retransmitting segments. - - It is possible to adjust TCP/IP's congestion limits by - altering the net.ipv4.tcp_reordering sysctl parameter. The - usual default value is 3. But keep in mind TCP stack is able - to automatically increase this when it detects reorders. - - Note that the fraction of packets that will be delivered out of - order is highly variable, and is unlikely to be zero. The level - of reordering depends upon a variety of factors, including the - networking interfaces, the switch, and the topology of the - configuration. Speaking in general terms, higher speed network - cards produce more reordering (due to factors such as packet - coalescing), and a "many to many" topology will reorder at a - higher rate than a "many slow to one fast" configuration. - - Many switches do not support any modes that stripe traffic - (instead choosing a port based upon IP or MAC level addresses); - for those devices, traffic for a particular connection flowing - through the switch to a balance-rr bond will not utilize greater - than one interface's worth of bandwidth. - - If you are utilizing protocols other than TCP/IP, UDP for - example, and your application can tolerate out of order - delivery, then this mode can allow for single stream datagram - performance that scales near linearly as interfaces are added - to the bond. - - This mode requires the switch to have the appropriate ports - configured for "etherchannel" or "trunking." - -active-backup: There is not much advantage in this network topology to - the active-backup mode, as the inactive backup devices are all - connected to the same peer as the primary. In this case, a - load balancing mode (with link monitoring) will provide the - same level of network availability, but with increased - available bandwidth. On the plus side, active-backup mode - does not require any configuration of the switch, so it may - have value if the hardware available does not support any of - the load balance modes. - -balance-xor: This mode will limit traffic such that packets destined - for specific peers will always be sent over the same - interface. Since the destination is determined by the MAC - addresses involved, this mode works best in a "local" network - configuration (as described above), with destinations all on - the same local network. This mode is likely to be suboptimal - if all your traffic is passed through a single router (i.e., a - "gatewayed" network configuration, as described above). - - As with balance-rr, the switch ports need to be configured for - "etherchannel" or "trunking." - -broadcast: Like active-backup, there is not much advantage to this - mode in this type of network topology. - -802.3ad: This mode can be a good choice for this type of network - topology. The 802.3ad mode is an IEEE standard, so all peers - that implement 802.3ad should interoperate well. The 802.3ad - protocol includes automatic configuration of the aggregates, - so minimal manual configuration of the switch is needed - (typically only to designate that some set of devices is - available for 802.3ad). The 802.3ad standard also mandates - that frames be delivered in order (within certain limits), so - in general single connections will not see misordering of - packets. The 802.3ad mode does have some drawbacks: the - standard mandates that all devices in the aggregate operate at - the same speed and duplex. Also, as with all bonding load - balance modes other than balance-rr, no single connection will - be able to utilize more than a single interface's worth of - bandwidth. - - Additionally, the linux bonding 802.3ad implementation - distributes traffic by peer (using an XOR of MAC addresses - and packet type ID), so in a "gatewayed" configuration, all - outgoing traffic will generally use the same device. Incoming - traffic may also end up on a single device, but that is - dependent upon the balancing policy of the peer's 802.3ad - implementation. In a "local" configuration, traffic will be - distributed across the devices in the bond. - - Finally, the 802.3ad mode mandates the use of the MII monitor, - therefore, the ARP monitor is not available in this mode. - -balance-tlb: The balance-tlb mode balances outgoing traffic by peer. - Since the balancing is done according to MAC address, in a - "gatewayed" configuration (as described above), this mode will - send all traffic across a single device. However, in a - "local" network configuration, this mode balances multiple - local network peers across devices in a vaguely intelligent - manner (not a simple XOR as in balance-xor or 802.3ad mode), - so that mathematically unlucky MAC addresses (i.e., ones that - XOR to the same value) will not all "bunch up" on a single - interface. - - Unlike 802.3ad, interfaces may be of differing speeds, and no - special switch configuration is required. On the down side, - in this mode all incoming traffic arrives over a single - interface, this mode requires certain ethtool support in the - network device driver of the slave interfaces, and the ARP - monitor is not available. - -balance-alb: This mode is everything that balance-tlb is, and more. - It has all of the features (and restrictions) of balance-tlb, - and will also balance incoming traffic from local network - peers (as described in the Bonding Module Options section, - above). - - The only additional down side to this mode is that the network - device driver must support changing the hardware address while - the device is open. - -12.1.2 MT Link Monitoring for Single Switch Topology ----------------------------------------------------- - - The choice of link monitoring may largely depend upon which -mode you choose to use. The more advanced load balancing modes do not -support the use of the ARP monitor, and are thus restricted to using -the MII monitor (which does not provide as high a level of end to end -assurance as the ARP monitor). - -12.2 Maximum Throughput in a Multiple Switch Topology ------------------------------------------------------ - - Multiple switches may be utilized to optimize for throughput -when they are configured in parallel as part of an isolated network -between two or more systems, for example: - - +-----------+ - | Host A | - +-+---+---+-+ - | | | - +--------+ | +---------+ - | | | - +------+---+ +-----+----+ +-----+----+ - | Switch A | | Switch B | | Switch C | - +------+---+ +-----+----+ +-----+----+ - | | | - +--------+ | +---------+ - | | | - +-+---+---+-+ - | Host B | - +-----------+ - - In this configuration, the switches are isolated from one -another. One reason to employ a topology such as this is for an -isolated network with many hosts (a cluster configured for high -performance, for example), using multiple smaller switches can be more -cost effective than a single larger switch, e.g., on a network with 24 -hosts, three 24 port switches can be significantly less expensive than -a single 72 port switch. - - If access beyond the network is required, an individual host -can be equipped with an additional network device connected to an -external network; this host then additionally acts as a gateway. - -12.2.1 MT Bonding Mode Selection for Multiple Switch Topology -------------------------------------------------------------- - - In actual practice, the bonding mode typically employed in -configurations of this type is balance-rr. Historically, in this -network configuration, the usual caveats about out of order packet -delivery are mitigated by the use of network adapters that do not do -any kind of packet coalescing (via the use of NAPI, or because the -device itself does not generate interrupts until some number of -packets has arrived). When employed in this fashion, the balance-rr -mode allows individual connections between two hosts to effectively -utilize greater than one interface's bandwidth. - -12.2.2 MT Link Monitoring for Multiple Switch Topology ------------------------------------------------------- - - Again, in actual practice, the MII monitor is most often used -in this configuration, as performance is given preference over -availability. The ARP monitor will function in this topology, but its -advantages over the MII monitor are mitigated by the volume of probes -needed as the number of systems involved grows (remember that each -host in the network is configured with bonding). - -13. Switch Behavior Issues -========================== - -13.1 Link Establishment and Failover Delays -------------------------------------------- - - Some switches exhibit undesirable behavior with regard to the -timing of link up and down reporting by the switch. - - First, when a link comes up, some switches may indicate that -the link is up (carrier available), but not pass traffic over the -interface for some period of time. This delay is typically due to -some type of autonegotiation or routing protocol, but may also occur -during switch initialization (e.g., during recovery after a switch -failure). If you find this to be a problem, specify an appropriate -value to the updelay bonding module option to delay the use of the -relevant interface(s). - - Second, some switches may "bounce" the link state one or more -times while a link is changing state. This occurs most commonly while -the switch is initializing. Again, an appropriate updelay value may -help. - - Note that when a bonding interface has no active links, the -driver will immediately reuse the first link that goes up, even if the -updelay parameter has been specified (the updelay is ignored in this -case). If there are slave interfaces waiting for the updelay timeout -to expire, the interface that first went into that state will be -immediately reused. This reduces down time of the network if the -value of updelay has been overestimated, and since this occurs only in -cases with no connectivity, there is no additional penalty for -ignoring the updelay. - - In addition to the concerns about switch timings, if your -switches take a long time to go into backup mode, it may be desirable -to not activate a backup interface immediately after a link goes down. -Failover may be delayed via the downdelay bonding module option. - -13.2 Duplicated Incoming Packets --------------------------------- - - NOTE: Starting with version 3.0.2, the bonding driver has logic to -suppress duplicate packets, which should largely eliminate this problem. -The following description is kept for reference. - - It is not uncommon to observe a short burst of duplicated -traffic when the bonding device is first used, or after it has been -idle for some period of time. This is most easily observed by issuing -a "ping" to some other host on the network, and noticing that the -output from ping flags duplicates (typically one per slave). - - For example, on a bond in active-backup mode with five slaves -all connected to one switch, the output may appear as follows: - -# ping -n 10.0.4.2 -PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data. -64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms -64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) -64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) -64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) -64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!) -64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms -64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms -64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms - - This is not due to an error in the bonding driver, rather, it -is a side effect of how many switches update their MAC forwarding -tables. Initially, the switch does not associate the MAC address in -the packet with a particular switch port, and so it may send the -traffic to all ports until its MAC forwarding table is updated. Since -the interfaces attached to the bond may occupy multiple ports on a -single switch, when the switch (temporarily) floods the traffic to all -ports, the bond device receives multiple copies of the same packet -(one per slave device). - - The duplicated packet behavior is switch dependent, some -switches exhibit this, and some do not. On switches that display this -behavior, it can be induced by clearing the MAC forwarding table (on -most Cisco switches, the privileged command "clear mac address-table -dynamic" will accomplish this). - -14. Hardware Specific Considerations -==================================== - - This section contains additional information for configuring -bonding on specific hardware platforms, or for interfacing bonding -with particular switches or other devices. - -14.1 IBM BladeCenter --------------------- - - This applies to the JS20 and similar systems. - - On the JS20 blades, the bonding driver supports only -balance-rr, active-backup, balance-tlb and balance-alb modes. This is -largely due to the network topology inside the BladeCenter, detailed -below. - -JS20 network adapter information --------------------------------- - - All JS20s come with two Broadcom Gigabit Ethernet ports -integrated on the planar (that's "motherboard" in IBM-speak). In the -BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to -I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2. -An add-on Broadcom daughter card can be installed on a JS20 to provide -two more Gigabit Ethernet ports. These ports, eth2 and eth3, are -wired to I/O Modules 3 and 4, respectively. - - Each I/O Module may contain either a switch or a passthrough -module (which allows ports to be directly connected to an external -switch). Some bonding modes require a specific BladeCenter internal -network topology in order to function; these are detailed below. - - Additional BladeCenter-specific networking information can be -found in two IBM Redbooks (www.ibm.com/redbooks): - -"IBM eServer BladeCenter Networking Options" -"IBM eServer BladeCenter Layer 2-7 Network Switching" - -BladeCenter networking configuration ------------------------------------- - - Because a BladeCenter can be configured in a very large number -of ways, this discussion will be confined to describing basic -configurations. - - Normally, Ethernet Switch Modules (ESMs) are used in I/O -modules 1 and 2. In this configuration, the eth0 and eth1 ports of a -JS20 will be connected to different internal switches (in the -respective I/O modules). - - A passthrough module (OPM or CPM, optical or copper, -passthrough module) connects the I/O module directly to an external -switch. By using PMs in I/O module #1 and #2, the eth0 and eth1 -interfaces of a JS20 can be redirected to the outside world and -connected to a common external switch. - - Depending upon the mix of ESMs and PMs, the network will -appear to bonding as either a single switch topology (all PMs) or as a -multiple switch topology (one or more ESMs, zero or more PMs). It is -also possible to connect ESMs together, resulting in a configuration -much like the example in "High Availability in a Multiple Switch -Topology," above. - -Requirements for specific modes -------------------------------- - - The balance-rr mode requires the use of passthrough modules -for devices in the bond, all connected to an common external switch. -That switch must be configured for "etherchannel" or "trunking" on the -appropriate ports, as is usual for balance-rr. - - The balance-alb and balance-tlb modes will function with -either switch modules or passthrough modules (or a mix). The only -specific requirement for these modes is that all network interfaces -must be able to reach all destinations for traffic sent over the -bonding device (i.e., the network must converge at some point outside -the BladeCenter). - - The active-backup mode has no additional requirements. - -Link monitoring issues ----------------------- - - When an Ethernet Switch Module is in place, only the ARP -monitor will reliably detect link loss to an external switch. This is -nothing unusual, but examination of the BladeCenter cabinet would -suggest that the "external" network ports are the ethernet ports for -the system, when it fact there is a switch between these "external" -ports and the devices on the JS20 system itself. The MII monitor is -only able to detect link failures between the ESM and the JS20 system. - - When a passthrough module is in place, the MII monitor does -detect failures to the "external" port, which is then directly -connected to the JS20 system. - -Other concerns --------------- - - The Serial Over LAN (SoL) link is established over the primary -ethernet (eth0) only, therefore, any loss of link to eth0 will result -in losing your SoL connection. It will not fail over with other -network traffic, as the SoL system is beyond the control of the -bonding driver. - - It may be desirable to disable spanning tree on the switch -(either the internal Ethernet Switch Module, or an external switch) to -avoid fail-over delay issues when using bonding. - - -15. Frequently Asked Questions -============================== - -1. Is it SMP safe? - - Yes. The old 2.0.xx channel bonding patch was not SMP safe. -The new driver was designed to be SMP safe from the start. - -2. What type of cards will work with it? - - Any Ethernet type cards (you can even mix cards - a Intel -EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes, -devices need not be of the same speed. - - Starting with version 3.2.1, bonding also supports Infiniband -slaves in active-backup mode. - -3. How many bonding devices can I have? - - There is no limit. - -4. How many slaves can a bonding device have? - - This is limited only by the number of network interfaces Linux -supports and/or the number of network cards you can place in your -system. - -5. What happens when a slave link dies? - - If link monitoring is enabled, then the failing device will be -disabled. The active-backup mode will fail over to a backup link, and -other modes will ignore the failed link. The link will continue to be -monitored, and should it recover, it will rejoin the bond (in whatever -manner is appropriate for the mode). See the sections on High -Availability and the documentation for each mode for additional -information. - - Link monitoring can be enabled via either the miimon or -arp_interval parameters (described in the module parameters section, -above). In general, miimon monitors the carrier state as sensed by -the underlying network device, and the arp monitor (arp_interval) -monitors connectivity to another host on the local network. - - If no link monitoring is configured, the bonding driver will -be unable to detect link failures, and will assume that all links are -always available. This will likely result in lost packets, and a -resulting degradation of performance. The precise performance loss -depends upon the bonding mode and network configuration. - -6. Can bonding be used for High Availability? - - Yes. See the section on High Availability for details. - -7. Which switches/systems does it work with? - - The full answer to this depends upon the desired mode. - - In the basic balance modes (balance-rr and balance-xor), it -works with any system that supports etherchannel (also called -trunking). Most managed switches currently available have such -support, and many unmanaged switches as well. - - The advanced balance modes (balance-tlb and balance-alb) do -not have special switch requirements, but do need device drivers that -support specific features (described in the appropriate section under -module parameters, above). - - In 802.3ad mode, it works with systems that support IEEE -802.3ad Dynamic Link Aggregation. Most managed and many unmanaged -switches currently available support 802.3ad. - - The active-backup mode should work with any Layer-II switch. - -8. Where does a bonding device get its MAC address from? - - When using slave devices that have fixed MAC addresses, or when -the fail_over_mac option is enabled, the bonding device's MAC address is -the MAC address of the active slave. - - For other configurations, if not explicitly configured (with -ifconfig or ip link), the MAC address of the bonding device is taken from -its first slave device. This MAC address is then passed to all following -slaves and remains persistent (even if the first slave is removed) until -the bonding device is brought down or reconfigured. - - If you wish to change the MAC address, you can set it with -ifconfig or ip link: - -# ifconfig bond0 hw ether 00:11:22:33:44:55 - -# ip link set bond0 address 66:77:88:99:aa:bb - - The MAC address can be also changed by bringing down/up the -device and then changing its slaves (or their order): - -# ifconfig bond0 down ; modprobe -r bonding -# ifconfig bond0 .... up -# ifenslave bond0 eth... - - This method will automatically take the address from the next -slave that is added. - - To restore your slaves' MAC addresses, you need to detach them -from the bond (`ifenslave -d bond0 eth0'). The bonding driver will -then restore the MAC addresses that the slaves had before they were -enslaved. - -16. Resources and Links -======================= - - The latest version of the bonding driver can be found in the latest -version of the linux kernel, found on http://kernel.org - - The latest version of this document can be found in the latest kernel -source (named Documentation/networking/bonding.txt). - - Discussions regarding the usage of the bonding driver take place on the -bonding-devel mailing list, hosted at sourceforge.net. If you have questions or -problems, post them to the list. The list address is: - -bonding-devel@lists.sourceforge.net - - The administrative interface (to subscribe or unsubscribe) can -be found at: - -https://lists.sourceforge.net/lists/listinfo/bonding-devel - - Discussions regarding the development of the bonding driver take place -on the main Linux network mailing list, hosted at vger.kernel.org. The list -address is: - -netdev@vger.kernel.org - - The administrative interface (to subscribe or unsubscribe) can -be found at: - -http://vger.kernel.org/vger-lists.html#netdev - -Donald Becker's Ethernet Drivers and diag programs may be found at : - - http://web.archive.org/web/*/http://www.scyld.com/network/ - -You will also find a lot of information regarding Ethernet, NWay, MII, -etc. at www.scyld.com. - --- END -- |