Linux Network Bonding

Every system and network administrator is responsible to provide a fast and non interrupted network connection for his users. One step in that direction is the easy to configure and reliable network bonding (also called network trunking) solution for linux systems.

The following configuration example is on a RedHat Enterprise Linux (RHEL) 5 System.

Network Scripts Configuration

mode = 0, load balancing round-robin (default);
miimon=500 (monitor bond all 500ms)

# vim /etc/sysconfig/network-scripts/ifcfg-bond0
DEVICE=bond0
BONDING_OPTS="mode=0 miimon=500"
BOOTPROTO=none
ONBOOT=yes
NETWORK=172.16.15.0
NETMASK=255.255.255.0
IPADDR=172.16.15.12
USERCTL=no

# vim /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no

# vim /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no


Load Channel Bonding modul on system boot


# vim /etc/modprobe.conf

alias bond0 bonding


Show Network Configuration

The bond MAC address will be the taken from its first slave device.

# ifconfig

bond0 Link encap:Ethernet HWaddr 00:0B:CD:E1:7C:B0
inet addr:172.16.15.12 Bcast:172.16.15.255 Mask:255.255.255.0
inet6 addr: fe80::20b:cdff:fee1:7cb0/64 Scope:Link
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
RX packets:1150 errors:0 dropped:0 overruns:0 frame:0
TX packets:127 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:168235 (164.2 KiB) TX bytes:22330 (21.8 KiB)

eth0 Link encap:Ethernet HWaddr 00:0B:CD:E1:7C:B0
inet6 addr: fe80::20b:cdff:fee1:7cb0/64 Scope:Link
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:567 errors:0 dropped:0 overruns:0 frame:0
TX packets:24 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:84522 (82.5 KiB) TX bytes:4639 (4.5 KiB)
Interrupt:201

eth1 Link encap:Ethernet HWaddr 00:0B:CD:E1:7C:B0
inet6 addr: fe80::20b:cdff:fee1:7cb0/64 Scope:Link
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:592 errors:0 dropped:0 overruns:0 frame:0
TX packets:113 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:84307 (82.3 KiB) TX bytes:19567 (19.1 KiB)
Interrupt:177 Base address:0x4000

Test the Bond

Plug out a network connection.

# tail -f /var/log/messages

kernel: bonding: bond0: link status definitely down for interface eth1, disabling it

Plug in the network connection again.

# tail -f /var/log/messages

kernel: bonding: bond0: link status definitely up for interface eth1.

The bonding module detects a failure in one of the two physical network interfaces configured in the bonding interface and disables the affected interface. After the failed network interface is online again the bonding module automatically re-integrates the interface into the bond. During this network interface failure, the logical network connection was always online and usable for all applications without any interrupts.