RHEL: Linux Bonding / Teaming Multiple Network Interfaces (NIC) Into a Single Interface

Step #1: Create a Bond0 Configuration File

Red Hat Enterprise Linux (and CentOS) stores network configuration in /etc/sysconfig/network-scripts/ directory.
First, you need to create a bond0 config file as follows:

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

Append the following linest:
DEVICE=bond0
IPADDR=192.168.1.20
NETWORK=192.168.1.0
NETMASK=255.255.255.0
USERCTL=no
BOOTPROTO=none
ONBOOT=yes

Replace IP address with your actual setup. Save and close the file.

Step #2: Modify eth0 and eth1 config files Open both configuration using a text editor such as vi/vim, and make sure file read as follows for eth0 interface

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

Modify/append directive as follows:
DEVICE=eth0
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

Open eth1 configuration file using vi text editor, enter:

# vi /etc/sysconfig/network-scripts/ifcfg-eth1

Make sure file read as follows for eth1 interface:
DEVICE=eth1
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

Save and close the file.

Step # 3: Load bond driver/module

Make sure bonding module is loaded when the channel-bonding interface (bond0) is brought up. Modify kernel modules configuration file:

# vi /etc/modprobe.conf

Append following two lines:
alias bond0 bonding
options bond0 mode=balance-alb miimon=100

 **********************************************************

Below are list of modes used in Network Bonding :

    balance-rr or 0 – round-robin mode for fault tolerance and load balancing.
    active-backup or 1 – Sets active-backup mode for fault tolerance.
    balance-xor or 2 – Sets an XOR (exclusive-or) mode for fault tolerance and load balancing.
    broadcast or 3 – Sets a broadcast mode for fault tolerance. All transmissions are sent on all slave interfaces.
    802.3ad or 4 – Sets an IEEE 802.3ad dynamic link aggregation mode. Creates aggregation groups that share the same
    speed & duplex settings.
    balance-tlb or 5 – Sets a Transmit Load Balancing (TLB) mode for fault tolerance & load balancing.
    balance-alb or 6 – Sets an Active Load Balancing (ALB) mode for fault tolerance & load balancing

************************************************************

Save file and exit to shell prompt. You can learn more about all bounding options by clicking here).

Step # 4: Test configuration

First, load the bonding module, enter:
# modprobe bonding

Restart the networking service in order to bring up bond0 interface, enter:
# service network restart

Make sure everything is working. Type the following cat command to query the current status of Linux kernel bounding driver, enter:

# cat /proc/net/bonding/bond0

Sample outputs:

Bonding Mode: load balancing (round-robin)
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 200
Down Delay (ms): 200
Slave Interface: eth0
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:0c:29:c6:be:59
Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:0c:29:c6:be:63

To list all network interfaces, enter:
# ifconfig

Sample outputs:

bond0     Link encap:Ethernet  HWaddr 00:0C:29:C6:BE:59
 inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
 inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
 UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
 RX packets:2804 errors:0 dropped:0 overruns:0 frame:0
 TX packets:1879 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0
 RX bytes:250825 (244.9 KiB)  TX bytes:244683 (238.9 KiB)
eth0      Link encap:Ethernet  HWaddr 00:0C:29:C6:BE:59
 inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
 inet6 addr: fe80::20c:29ff:fec6:be59/64 Scope:Link
 UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
 RX packets:2809 errors:0 dropped:0 overruns:0 frame:0
 TX packets:1390 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000
 RX bytes:251161 (245.2 KiB)  TX bytes:180289 (176.0 KiB)
 Interrupt:11 Base address:0x1400
eth1      Link encap:Ethernet  HWaddr 00:0C:29:C6:BE:59
 inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
 inet6 addr: fe80::20c:29ff:fec6:be59/64 Scope:Link
 UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
 RX packets:4 errors:0 dropped:0 overruns:0 frame:0
 TX packets:502 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000
 RX bytes:258 (258.0 b)  TX bytes:66516 (64.9 KiB)
 Interrupt:10 Base address:0x1480