Nasser Heidari

2009-07-31

Linux Ethernet Bonding

Filed under: Linux — Nasser Heidari @ 18:31

Bonding allows you to aggregate multiple ports into a single group, effectively combining the bandwidth into a single connection. Bonding also allows you to create multi-gigabit pipes to transport traffic through the highest traffic areas of your network. For example, you can aggregate three megabits ports (1 mb each) into a three-megabits trunk port. That is equivalent with having one interface with three megabits speed.
You can use it wherever you need redundant links, fault tolerance or load balancing networks. It is the best way to have a high availability network segment. A very useful way to use bonding is to use it in connection with 802.1q VLAN support (your network equipment must have 802.1q protocol implemented).

In order to configure Ethernet bonding, the kernel must have support for bonding:

# modprobe --list | grep bonding

/lib/modules/2.6.26-2-686/kernel/drivers/net/bonding/bonding.ko

Then :

# modprobe bonding mode=0 miimon=50 # load bonding module # ifconfig eth0 down # putting down the eth0 interface # ifconfig eth1 down # putting down the eth1 interface # ifconfig bond0 hw ether 00:12:34:56:78:90 # changing the MAC address of the bond0 interface # ifconfig bond0 192.168.0.254 up # to set ethX interfaces as slave the bond0 must have an ip. # ifenslave bond0 eth0 eth1 # putting the eth0 and eth1 interface in the slave mod for bond0

Now you can configuration by entering this command :

# cat /proc/net/bonding/bond0

Ethernet Channel Bonding Driver: v3.2.5 (March 21, 2008)

Bonding Mode: load balancing (round-robin)
MII Status: up
MII Polling Interval (ms): 50
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth0
MII Status: up
Link Failure Count: 1
Permanent HW addr: 08:00:27:d7:a8:cb

Slave Interface: eth1
MII Status: up
Link Failure Count: 1
Permanent HW addr: 08:00:27:a9:e3:bf

You can set up your bond interface according to your needs. Changing one parameters (mode=X) you can have the following bonding types:
mode=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.

mode=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.

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.

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

mode=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:
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.

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.

mode=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.

The most used are the first four mode types…

For more information , refer to these pages :
http://sourceforge.net/projects/bonding
http://linux-ip.net/html/ether-bonding.html
http://www.linuxfoundation.org/en/Net:Bonding
http://www.linuxhorizon.ro/bonding.html
http://www.howtoforge.com/nic_bonding

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