NIC Bonding

                             

Meaning:-

        The concept of NIC Bonding (or sometimes called NIC Teaming) is that you have two NICs bonded together to appear as if they are the same physical device. I.e. They will both present the same Hardware (MAC) address. This is accomplished through the ifenslave utility, which enables the kernel to see/use only one device.

NIC Bonding also be known as:

* “NIC Aggregation” (Mainly Linux world)
* “NIC Teaming” (Mainly Windows world)
* “Port Trunking” (Mainly hardware world)
                             
        It provides increased bandwidth by merging the bandwidth of the individual ports/NICs.It’s primary use _is_ to increase a network link speed beyond the limits of any one single cable or port. Although It can also be used for failover, if one link dies all traffic to and from the machine should be routed to the remaining links.

        The “ifenslave” is a tool to attach and detach slave network interfaces to a bonding device. A bonding device will act like a normal Ethernet network device to the kernel, but will send out the packets via the slave devices using a simple round-robin scheduler. This allows you a simple load-balancing.

NIC Bonding Prerequiest :-

      You must have an bonding support in your kernel, so you can check with following.

$ modprobe -l | grep bonding
/lib/modules/2.6.9-55.ELsmp/kernel/drivers/net/bonding/bonding.ko

$ cat /boot/config-2.6.9-55.EL | grep -i bonding
CONFIG_BONDING=m

NIC Bonding Configuration :-

(1) The “modprob.conf” file should include the followings 3 lines.

$ cat /etc/modprobe.conf

alias bond0 bonding
options bond0 max_bonds=2 miimon=100 mode=1
options bond1 miimon=100 mode=1

Here:
      max_bonds = ” The number of bonding devices to create for this instance of the bonding driver e.g., if max_bonds is 3, and the bonding driver is not already loaded, then bond0,
bond1 and bond2 will be created. The default value is 1.”

      miimon = ” Specifies the MII link monitoring frequency in milliseconds.This determines how often the link state of each slave is inspected for link failures. A value of zero
disables MII link monitoring. A value of 100 is a good starting point.”

      mode = ” Specifies one of the bonding policies. The default is balance-rr (round robin).”
      Possible values are:

0 = Round-robin policy: Transmit packets in sequential order from the first slave
through the last.

1 = Active-backup policy: Only one slave in the bond is active. A different slave
becomes active if, and only if, the active slave fails.

2 = Tries to balance traffic by splitting up outgoing packets between the adapters,
using the same one for each specific destination when possible.

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

(2) You will have to add the following to do a working NIC Bonding.

$ vi /etc/sysconfig/network-scripts/ifcfg-bond0

## Now add the following things to the above file. ##

DEVICE=bond0
BOOTPROTO=none
ONBOOT=yes
NETWORK=
NETMASK=
IPADDR=
GATEWAY=
USERCTL=no

(3) Now just append the following lines to (eth0).

$ vi /etc/sysconfig/network-scripts/ifcfg-eth0

## nOW APPEND the following to the above file. ##

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=none
MASTER=bond0
SLAVE=yes
USERCTL=no

(4) Now just append the following lines to (eth1).

$  /etc/sysconfig/network-scripts/ifcfg-eth1

## nOW APPEND the following to the above file. ##

DEVICE=eth1
ONBOOT=yes
BOOTPROTO=none
MASTER=bond0
SLAVE=yes
USERCTL=no