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EtherChannel in Linux aka adapter bonding

Bonding? What is it? Well, this is EtherChannel spoken in LINUX. To configure it, a host has to have at least two Ethernet adapters. If not sure what adapter is connected with the network you can turn it identification light on executing the next command which will “illuminate” the eth3 (in this case) for fifteen seconds.

# ethtool -p eth3 15

The last command will turn the light off ent3 interface after fifteen seconds. If NIC does not have ID light (led), pull out its network cable and watch the /var/log/messages file for the appropriate entry – they will tell you what NIC lost network connectivity.

The reset is very simple. In LINUX, it seems that it is customary to name the “bonded” adapters bond followed with a digit. For example the first “bonded” adapter is called bond0.

To configure it, execute the following steps:

a. Move to the /etc/sysconfig/network-scripts directory and edit appropriate ifcfg-* files to contain the following lines (the ifcfg-eth0 shown)


It is the MASTER statement that identifies the adapters common (bonded) entity which in this case is ifcfg-bond0.

b. edit the ifcfg-bond0 to contain the following:

BONDING_OPTS="mode=1 miimon=1000"

The values associated with addresses, netmask and gateway are site dependent and in your case will be different. The BONDING_OPTS entry defines a space delimited list of the bonded adapter parameters:

miimon Specifies (in milliseconds) how often MII link monitoring occurs.
mode=1 Sets an active-backup policy for fault tolerance.

At boot time, to automatically load code making the bonded adapters possible, we have to make sure to create the file in /etc/modprobe.d called bind0.conf which contains one line:

alias bond0 bonding

Finally, restart the network service.

# service network restart

And verify that bond0 has the right components and IP address execute the next command.

# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc mq master bond0 state UP qlen 1000
    link/ether ac:16:2d:89:4e:0c brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc mq master bond0 state UP qlen 1000
    link/ether ac:16:2d:89:4e:0c brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether ac:16:2d:89:4e:0e brd ff:ff:ff:ff:ff:ff
5: eth3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether ac:16:2d:89:4e:0f brd ff:ff:ff:ff:ff:ff
6: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
    link/ether ac:16:2d:89:4e:0c brd ff:ff:ff:ff:ff:ff
    inet brd scope global bond0
    inet6 fe80::ae16:2dff:fe89:4e0c/64 scope link
       valid_lft forever preferred_lft forever

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