Chapter 4. Configure Network Bonding

Red Hat Enterprise Linux 7 allows administrators to bind multiple network interfaces together into a single, bonded, channel. Channel bonding enables two or more network interfaces to act as one, simultaneously increasing the bandwidth and providing redundancy.

Warning

The use of direct cable connections without network switches is not supported for bonding. The failover mechanisms described here will not work as expected without the presence of network switches. See the Red Hat Knowledgebase article Why is bonding in not supported with direct connection using crossover cables? for more information.

Note

The active-backup, balance-tlb and balance-alb modes do not require any specific configuration of the switch. Other bonding modes require configuring the switch to aggregate the links. For example, a Cisco switch requires EtherChannel for Modes 0, 2, and 3, but for Mode 4 LACP and EtherChannel are required. See the documentation supplied with your switch and see https://www.kernel.org/doc/Documentation/networking/bonding.txt

4.1. Understanding the Default Behavior of Master and Slave Interfaces

When controlling bonded slave interfaces using the NetworkManager daemon, and especially when fault finding, keep the following in mind:
  1. Starting the master interface does not automatically start the slave interfaces.
  2. Starting a slave interface always starts the master interface.
  3. Stopping the master interface also stops the slave interfaces.
  4. A master without slaves can start static IP connections.
  5. A master without slaves waits for slaves when starting DHCP connections.
  6. A master with a DHCP connection waiting for slaves completes when a slave with a carrier is added.
  7. A master with a DHCP connection waiting for slaves continues waiting when a slave without a carrier is added.