High Available NICs. Also known as Link Aggregation, channel bonding, or trunking. This configuration will allow for the failure of one interface or connection and continue with overall functionality. By changing the bonding options, you can change the bonding type to round robin, aggregation or various other types. For this guide, I am doing active-backup.
This reference is for Centos5/Redhat5/Fedora or greater. Recent releases have changed link bonding and modprobe so this exact configuration will not work on older distros or releases.
Create a new file /etc/modprobe.d/bonding.conf and only include the following.
alias bond0 bonding
Configure your two interfaces as slaves to the master we will create.
For your first interface /etc/sysconfig/network-scripts/ifcfg-eth0:
DEVICE="eth0" NM_CONTROLLED="no" ONBOOT="yes" BOOTPROTO=none MASTER=bond0 SLAVE=yes USERCTL=no
For your second interface /etc/sysconfig/network-scripts/ifcfg-eth1:
DEVICE="eth1" NM_CONTROLLED="no" ONBOOT="yes" BOOTPROTO=none MASTER=bond0 SLAVE=yes USERCTL=no
And now, create the master bond0. Create the file /etc/sysconfig/network-scripts/ifcfg-bond0. You will notice now that the BONDING_OPTS are located in the config file and no longer in the /etc/modprobe.conf.
DEVICE="bond0" NM_CONTROLLED="no" ONBOOT="yes" BOOTPROTO=none USERCTL=no BONDING_OPTS="miimon=1000 mode=active-backup" IPADDR=126.96.36.199 SUBNET=255.255.255.0 GATEWAY=188.8.131.52
Now, restart the network configuration.
service network restart
You can check the configuration now with:
You should see something like
Ethernet Channel Bonding Driver: v3.6.0 (September 26, 2009) Bonding Mode: fault-tolerance (active-backup) Primary Slave: None Currently Active Slave: eth1 MII Status: up MII Polling Interval (ms): 1000 Up Delay (ms): 0 Down Delay (ms): 0 Slave Interface: eth0 MII Status: up Speed: 1000 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:25:90:64:a4:77 Slave queue ID: 0 Slave Interface: eth1 MII Status: up Speed: 1000 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:25:90:66:89:9c Slave queue ID: 0