Bonding Multiple NICs

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This tutorial will show you how to setup a bond where multiple network cards are combined to look like a single NIC for increased throughput and redundancy.

Ubuntu 10.04 or higher

  • Install ifenslave
sudo apt-get update && sudo apt-get install ifenslave

We are using a basic bonding mode 2. For other modes, please see:

We have had issues on Ubuntu 10.04 using mode 0, we have had better luck using mode 2

mode=0 (balance-rr) (See note above!)

Round-robin policy: Stripes traffic across multiple interfaces. This mode provides load balancing and fault tolerance. the striping generally results in peer systems receiving packets out of order, causing TCP/IP’s congestion control system to kick in, often by retransmitting segments.

mode=1 (active-backup)

Active-backup policy: Only one slave in the bond is active. A different slave becomes active if, and only if, 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. The primary option affects the behavior of this mode.

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.

  • Edit your interfaces file, /etc/network/interfaces.
auto lo
iface lo inet loopback
auto bond0
iface bond0 inet static
   bond-slaves none
   bond-mode 2
   bond-miimon 100
   hwaddress ether 00:AA:BB:CC:DD:EE
auto eth0
iface eth0 inet manual
   bond-master bond0
   bond-primary eth0 eth1
auto eth1
iface eth1 inet manual
   bond-master bond0
   bond-primary eth0 eth1

hwaddress could be the MAC address of one of you network cards, this can be found by running:

  • Reboot your server
sudo reboot

CentOS / RedHat

Edit /etc/modprobe.conf and add the following (see the note above in the Ubuntu section about this type of bonding):

alias bond0 bonding
options bonding mode=0 miimon=100 downdelay=200 updelay=200

Create the file /etc/sysconfig/network-scripts/ifcfg-bond0 and add the following (substitute your server's IP address, netmask and gateway of course):

# Bonded interface
IPADDR=<Your server IP here>
NETMASK=<Your netmask>
GATEWAY=<Your server's default gateway>

Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 so that it looks similar to this. This file should already exist, you're just editing out the IP address configuration. Preserve your server's MAC address if this file is already there to make things easier.

HWADDR=<MAC address of NIC>

Edit /etc/sysconfig/network-scripts/ifcfg-eth1 and so on for each interface you want to bond together. All that's needed in the ifcfg script is what is shown above. Again, substitute your server's MAC addresses in place of the HWADDR listed above. Don't forget to change the DEVICE= line as well to correspond to the interface you're setting up (eth1, eth2, etc)