Linux Basics: Create Network Bonding On Debian 7 / Ubuntu 13.10

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What is network bonding?

Network bonding is a method of combining (joining) two or more network interfaces together into a single interface. It will increase the network throughput, bandwidth and give redundancy. If one interface is down or unplugged, the other one will keep the network traffic alive. Network bonding can be used in situations wherever you need redundancy, fault tolerance or load balancing networks.

Linux allows us to bond multiple network interfaces into single interface using a special kernel module named bonding. The Linux bonding driver provides a method for combining 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.

Types of Network Bonding

According the to the official documentation, here is the types of network bonding modes.

mode=0 (balance-rr)

Round-robin policy: It the default mode. It transmits packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

mode=1 (active-backup)

Active-backup policy: In this mode, only one slave in the bond is active. The other one will become active, only when the active slave fails. The bond’s MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. This mode provides fault tolerance.

mode=2 (balance-xor)

XOR policy: Transmit based on [(source MAC address XOR'd with destination MAC address) modulo slave count]. This selects the same slave for each destination MAC address. This mode provides load balancing and fault tolerance.

mode=3 (broadcast)

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

mode=4 (802.3ad)

IEEE 802.3ad Dynamic link aggregation. Creates aggregation groups that share the same speed and duplex settings. Utilizes all slaves in the active aggregator according to the 802.3ad specification.

Prerequisites:

- Ethtool support in the base drivers for retrieving the speed and duplex of each slave.
- A switch that supports IEEE 802.3ad Dynamic link aggregation. Most switches will require some type of configuration to enable 802.3ad mode.

mode=5 (balance-tlb)

Adaptive transmit load balancing: channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave.

Prerequisite:

- Ethtool support in the base drivers for retrieving the speed of each slave.

mode=6 (balance-alb)

Adaptive load balancing: includes balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special switch support. The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond such that different peers use different hardware addresses for the server.

Setup Network Bonding On Debian 7 / Ubuntu 13.10 Desktop

In this handy tutorial let us see how to setup network bonding on Debian 7. Though it was tested on Debian 7, it should work on Ubuntu and its derivatives.

We need atleast two or more network cards.

I have three network interfaces, namely eth0, eth1 and eth2 in my Debian 7 LXDE desktop. Let us combine two NICs (eth1 and eth2) and make them into one NIC named bond0.

Install Bonding Kernel Module

First, we have to install bonding kernel module using the command:

# apt-get install ifenslave-2.6

Before going further, stop networking service.

# /etc/init.d/networking stop

Warning: You should not enter the above command over SSH connection.

Configure Bond0 Interface

First, let us create a bond0 configuration file as shown below.

Go to the directory where Debian/Ubuntu stores the network configuration files. By default, Debian and its derivatives stores the network configuration files under /etc/network/ directory.

Create bond0 configuration file under the above mentioned directory.

# vi /etc/network/interfaces

Add the following lines marked in red color to create network bond for eth1 and eth2.

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The first network bond
auto bond0
iface bond0 inet static
address 192.168.1.200
netmask 255.255.255.0
gateway 192.168.1.1
slaves eth1 eth2
bond-mode 1
bond-miimon 100
bond_downdelay 200
bond_updelay 200

Save and close file. 

Note: Here we will be configuring mode1(active-backup). 192.168.1.200 is bond0 IP address.

Next we have to load up the bond0 interface into the kernel. To do that, create a new file /etc/modprobe.d/bonding.conf,

# vi /etc/modprobe.d/bonding.conf

Add the following line in it.

alias bond0 bonding
options bonding mode=1 arp_interval=2000 arp_ip_target=192.168.1.1

Warning: Without this file, you’ll get warning message when you restart network service. Here 192.168.1.1 is my router(gateway) ip address. Save and close the file.

Now let us enable the bonding kernel module, using the command:

# modprobe -v options bonding mode=1 arp_interval=2000 arp_ip_target=192.168.1.1

Next Start/Restart network service to take effect the changes.

# service network start

Test Network Bonding

Now enter the following command to check whether the bonding interface bond0 is up and running:

# cat /proc/net/bonding/bond0

Sample output:

Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)

Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth1
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 200
Down Delay (ms): 200

Slave Interface: eth1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 08:00:27:16:07:6a
Slave queue ID: 0

Slave Interface: eth2
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 08:00:27:60:18:bb
Slave queue ID: 0

As you see in the above output, the bond0 interface is up and running and it is configured as active-backup(mode1) mode. In this mode, only one slave in the bond is active. The other one will become active, only when the active slave fails.

To view the list of network interfaces and their IP address, enter the following command:

# ifconfig

Sample output:

bond0     Link encap:Ethernet  HWaddr 08:00:27:16:07:6a  
          inet addr:192.168.1.200  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe16:76a/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:114 errors:0 dropped:31 overruns:0 frame:0
          TX packets:197 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:14269 (13.9 KiB)  TX bytes:29286 (28.5 KiB)

eth0      Link encap:Ethernet  HWaddr 08:00:27:ac:65:e9  
          inet addr:192.168.1.102  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:feac:65e9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1164 errors:0 dropped:0 overruns:0 frame:0
          TX packets:42 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:89712 (87.6 KiB)  TX bytes:8706 (8.5 KiB)

eth1      Link encap:Ethernet  HWaddr 08:00:27:16:07:6a  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:77 errors:0 dropped:0 overruns:0 frame:0
          TX packets:197 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:11459 (11.1 KiB)  TX bytes:29286 (28.5 KiB)

eth2      Link encap:Ethernet  HWaddr 08:00:27:16:07:6a  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:37 errors:0 dropped:31 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2810 (2.7 KiB)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  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:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

As per the above output, bond0 is configured as master; eth1 and eth2 are configured as a slave.

Want to create network bonding on RHEL based systems, check out our previous article.

Source & Reference Links:

- Kernel Documentation page

For questions please refer to our Q/A forum at : http://ask.unixmen.com/

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