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NIC Channel Bonding in Linux

Today I had implemented NIC bonding (bind both NIC so that it works as a single device). Bonding is nothing but Linux kernel feature that allows to aggregate multiple like interfaces (such as eth0, eth1) into a single virtual link such as bond0. The idea is pretty simple get higher data rates and as well as link failover. NIC channel bonding allows multiple network cards to act as one, allowing increased bandwidth and redundancy.


Linux allows binding of multiple network interfaces into a single channel/NIC using special kernel module called bonding. According to official bonding documentation:

The Linux bonding driver provides a method for aggregating multiple network interfaces into a single logical "bonded" interface. The behavior of the bonded interfaces depends upon the mode; generally speaking, modes provide either hot standby or load balancing services. Additionally, link integrity monitoring may be performed.

Step #1: Create a Bond0 Configuration File


Red Hat Enterprise Linux (and its clone such as 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
 
You need to 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. You need to modify kernel modules configuration file:

# vi /etc/modprobe.conf
Append following two lines:

alias bond0 bonding
options bond0 mode=balance-alb miimon=100
Save file and exit to shell prompt. A description of the bonding options is available 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 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

Once the bond is configured it acts like any other Ethernet device. For example, you can configure alias interfaces to handle multiple IP addresses, as shown below.

Create the "ifcfg-bond0:1" and "ifcfg-bond0:2" files in the "/etc/sysconfig/network-scripts" directory with the following contents.

# ifcfg-bond0:1 file contents
DEVICE=bond0:1
BOOTPROTO=none
ONBOOT=yes
NETWORK=192.168.0.0
NETMASK=255.255.255.0
IPADDR=192.168.0.172
USERCTL=no
BONDING_OPTS="mode=1 miimon=100"

# ifcfg-bond0:2 file contents
DEVICE=bond0:2
BOOTPROTO=none
ONBOOT=yes
NETWORK=192.168.0.0
NETMASK=255.255.255.0
IPADDR=192.168.0.173
USERCTL=no
BONDING_OPTS="mode=1 miimon=100"


Notice, the device names and IP addresses differ from the original "ifcfg-bond0" file.

Restart the network service for the changes to take effect.
# service network restart
Shutting down interface bond0:                             [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface bond0:                               [  OK  ]
#
The ifconfig command shows the three IP addresses being handled by the bond.
[root@wls11g-1 network-scripts]# ifconfig
bond0     Link encap:Ethernet  HWaddr 08:00:27:FC:F5:B7  
          inet addr:192.168.0.171  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:14635 errors:0 dropped:306 overruns:0 frame:0
          TX packets:7310 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:17571270 (16.7 MiB)  TX bytes:554475 (541.4 KiB)

bond0:1   Link encap:Ethernet  HWaddr 08:00:27:FC:F5:B7  
          inet addr:192.168.0.172  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

bond0:2   Link encap:Ethernet  HWaddr 08:00:27:FC:F5:B7  
          inet addr:192.168.0.173  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

eth0      Link encap:Ethernet  HWaddr 08:00:27:FC:F5:B7  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:1835 errors:0 dropped:0 overruns:0 frame:0
          TX packets:961 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:189616 (185.1 KiB)  TX bytes:129841 (126.7 KiB)

eth1      Link encap:Ethernet  HWaddr 08:00:27:FC:F5:B7  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:12800 errors:0 dropped:306 overruns:0 frame:0
          TX packets:6349 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:17381654 (16.5 MiB)  TX bytes:424634 (414.6 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:1541 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1541 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:3612733 (3.4 MiB)  TX bytes:3612733 (3.4 MiB)

#
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