How to Setup Network bonding in Linux

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How to Setup Network bonding

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.

Read more: Basic Linux Networking Command

Create a bond0 configuration file

Red Hat Linux stores network configuration in /etc/sysconfig/network-scripts/ directory. First, you need to create bond0 config file:

# vi /etc/sysconfig/network-scripts/ifcfg-bond0
Append following lines to it:
 DEVICE=bond0
 IPADDR=192.168.0.14
 NETWORK=192.168.0.3
 NETMASK=255.255.255.0
 USERCTL=no
 BOOTPROTO=none
 ONBOOT=yes

Make sure you are replacing above IP address with your server/system IP address.

Modify eth0 and eth1 inferface config files:

Open both configuration using vi text editor 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

Next open eth1 configuration file using your favorite editor:

# vi /etc/sysconfig/network-scripts/ifcfg-eth1
Change the file with your bond detail like below;
 DEVICE=eth1
 USERCTL=no
 ONBOOT=yes
 MASTER=bond0
 SLAVE=yes
 BOOTPROTO=none

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: (Append following two lines). Refer other Modes of Bonding End of the Document.

# vi /etc/modprobe.conf
 alias bond0 bonding
 options bond0 mode=balance-alb miimon=100

Test configuration

First, load the bonding module:

# modprobe bonding

Restart networking service in order to bring up bond0 interface:

# service network restart

Verify everything is working:

# less /proc/net/bonding/bond0

Bonding Mode: load balancing (round-robin)
MII Status: up
MII Polling Interval (ms): 0
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth0
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:50:56:BC:FE:AE

Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:50:56:BC:FE:AE

List all interfaces:

# ifconfig
 bond0  Link encap:Ethernet  HWaddr 00:50:56:BC:FE:AE
 inet addr:192.168.0.161  Bcast:192.168.0.255  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

 eth0  Link encap:Ethernet  HWaddr 00:50:56:BC:FE:AE
 inet addr:192.168.0.161  Bcast:192.168.0.255  Mask:255.255.255.0
 inet6 addr: fe80::183e:6aff:feac:a001/64 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

 eth1  Link encap:Ethernet  HWaddr 00:50:56:BC:FE:AE
 inet addr:192.168.0.161  Bcast:192.168.0.255  Mask:255.255.255.0
 inet6 addr: fe80::250:56ff:febc:feae/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

Modes of bonding :

RHEL bonding supports 7 possible “modes” for bonded interfaces. These modes determine the way in which traffic sent out of the bonded interface is actually dispersed over the real interfaces. Modes 0, 1, and 2 are by far the most commonly used among them.

  • Mode 0 (balance-rr)
    This mode transmits packets in a sequential order from the first available slave through the last. If two real interfaces are slaves in the bond and two packets arrive destined out of the bonded interface the first will be transmitted on the first slave and the second frame will be transmitted on the second slave. The third packet will be sent on the first and so on. This provides load balancing and fault tolerance.
  • Mode 1 (active-backup)
    Mode 1 places one of the interfaces into a backup state and will only make it active if the link is lost by the active interface. Only one slave in the bond is active at an instance of time. A different slave becomes active only when the active slave fails. This mode provides fault tolerance.
  • Mode 2 (balance-xor)
    Transmits based on XOR formula. (Source MAC address is XOR’d with destination MAC address) modula slave count. This selects the same slave for each destination MAC address and provides load balancing and fault tolerance.
  • Mode 3 (broadcast)
    The broadcast mode transmits everything on all slave interfaces. This mode is least used (only for specific purpose) and provides only fault tolerance.
  • Mode 4 (802.3ad)
    The 802.3ad mode is known as Dynamic Link Aggregation mode. It creates aggregation groups that share the same speed and duplex settings. This mode requires a switch that supports IEEE 802.3ad Dynamic link. Slave selection for outgoing traffic is done according to the transmit hash policy, which may be changed from the default simple XOR policy via the xmit_hash_policy option. Note that not all transmit policies may be 802.3ad compliant, particularly in regards to the packet misordering requirements of section 43.2.4 of the 802.3ad standard. Differing peer implementations will have varying tolerances for noncompliance.
  • Mode 5 (balance-tlb)
    This is called as Adaptive transmit load balancing. The outgoing traffic is distributed according to the current load and queue on each slave interface. Incoming traffic is received by the current slave.
  • Mode 6 (balance-alb)
    This is Adaptive load balancing mode. This includes balance-tlb + receive load balancing (rlb) for IPV4 traffic. The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the server on their way out and overwrites the src hw address with the unique hw address of one of the slaves in the bond such that different clients use different hw addresses for the server.

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