Network Bonding

Assuming two network interfaces eth0 and eth1 as shown below.

[root@samserv05 network-scripts]# ifconfig -a
eth0      Link encap:Ethernet  HWaddr D8:D3:85:5F:D1:B6
          inet addr:172.28.7.206  Bcast:172.28.7.255  Mask:255.255.255.128
          inet6 addr: fe80::dad3:85ff:fe5f:d1b6/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:744339 errors:0 dropped:0 overruns:0 frame:0
          TX packets:234404 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:638166148 (608.6 MiB)  TX bytes:37473617 (35.7 MiB)
          Memory:fbd60000-fbd80000
eth1      Link encap:Ethernet  HWaddr D8:D3:85:5F:D1:B7
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Memory:fbde0000-fbe00000
1. Edit modprob.conf and append “alias bond0 bonding” as shown below.
Vi  /etc/modprob.conf
alias bond0 bonding
2. Create bond0 file and append below entry in it. Change the IPADDR and NETMASK to the one on your server
cd /etc/sysconfig/network-scripts/
cp ifcfg-eth0 ifcfg-eth1 /var/tmp
vi  etc/sysconfig/network-scripts/ifcfg-bond0
ifcfg-bond0
DEVICE=bond0
IPADDR=172.28.38.134
NETMASK=255.255.254.0
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
BONDING_OPTS="mode=active-backup miimon=100"


3. Edit eth0 and eth1 and append the content below. Replace HWADDR with the hardware address on your servers
Ifcg-eth0
DEVICE=eth0
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none
ETHTOOL_OPTS="speed 1000 duplex full"
HWADDR=00:17:A4:78:5C:B9
Ifcfg-eth1
DEVICE=eth1
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none
ETHTOOL_OPTS="speed 1000 duplex full"
HWADDR=D8:D3:85:5D:F1:C7
4. Run the command below from the console
First down the active eth, e.g. eth0
Ifconfig eth0 down
/etc/init.d/network restart 
[root@samserv05 network-scripts]# cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v3.4.0-1 (October 7, 2008)
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
Speed: 100 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: d8:d3:85:5f:d1:b6
Slave Interface: eth1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 1
Permanent HW addr: d8:d3:85:5d:f1:c7
If this does not work, reboot the server.