NIC-Bonding

Active-Backup Bonding with Linux
Bonding is also called port trunking or link aggregation and it will let you combine several network ports to make a single group.
This combines the the bandwidth from several interfaces as a “single connection”.
There are the different modes of ethernet bonding:

0 (balance-rr) Round-robin policy: Transmit packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

1 (active-backup) 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. This mode provides fault tolerance. The primary option affects the behavior of this mode.

2 (balance-xor) XOR policy: Transmit based on [(source MAC address XOR’d with destination MAC address) modulo slave count]. This selects the same slave for each destination MAC address. This mode provides load balancing and fault tolerance.

3 (broadcast) Broadcast policy: transmits everything on all slave interfaces. This mode provides fault tolerance.

4 (802.3ad) 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.
(Pre-requisites: Ethtool support in the base drivers for retrieving the speed and duplex of each slave. A switch that supports IEEE 802.3ad Dynamic link aggregation. Most switches will require some type of configuration to enable 802.3ad mode.)


5 (balance-tlb) Adaptive transmit load balancing: channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. 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.)


6 (balance-alb) 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.

In order to configure “active-backup” bonding (what I needed on my setup) on a two-interface environment, I used the following settings (Ubuntu 10.10):
vim /etc/network/interfaces
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auto bond0
 iface bond0 inet static
 address 192.168.0.1
 netmask 255.255.255.0
 gateway 192.168.0.254
 bond-slaves eth0 eth1
 bond_mode active-backup
 bond_miimon 100

bond_* configuration parameters follows:
bond_mode: set the bonding mode (see previous list).
bond_primary: choose the primary slave iface_name (used with mode active-backup).
bond_miimon: mii monitoring frequency (in ms).
bond_updelay: amount of time (ms) before enabling a slave after a link recovery has been detected.
bond_downdelay: amount of time (ms) before disabling a slave after a link failure has been detected.
bond_arp_ip_target: the IP addresses to use as ARP monitoring peers when arp_interval is > 0.
bond_arp_interval: ARP link monitoring frequency.
bond_xmit_hash_policy: the transmit hash policy (layer2, layer3+4 – use with bond_mode balance-xor / 802.3ad).
bond_lacp_rate: rate in which we’ll ask our link partner to transmit LACPDU packets (slow: 30 seconds, fast: 1 second – 802.3ad mode only).
To check if all is working correctly, simply:
cat /proc/net/bonding/bond0
and check the bonding is working correctly:
Ethernet Channel Bonding Driver: v3.6.0 (September 26, 2009)

Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth0
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth0
MII Status: up
Link Failure Count: 0
Permanent HW addr: XX:XX:XX:XX:XX:XX

Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: XX:XX:XX:XX:XX:XX
(also check the interface bond0 is up and running with all needed active services)



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