Reference Guide

Figure 57. Configuring Redundant Layer 2 Pairs without Spanning Tree
You configure a redundant pair by assigning a backup interface to a primary interface with the switchport backup
interface command. Initially, the primary interface is active and transmits traffic and the backup interface remains
down. If the primary fails for any reason, the backup transitions to an active Up state. If the primary interface fails and
later comes back up, it remains as the backup interface for the redundant pair.
FTOS supports only Gigabit, 10 Gigabit, and 40-Gigabit ports and port channels as primary/backup interfaces in
redundant pairs. (A port channel is also referred to as a link aggregation group (LAG). For more information, refer to
Interfaces) If the interface is a member link of a LAG, the following primary/backup interfaces are also supported:
• primary interface is a physical interface, the backup interface can be a physical interface
• primary interface is a physical interface, the backup interface can be a static or dynamic LAG
• primary interface is a static or dynamic LAG, the backup interface can be a physical interface
• primary interface is a static or dynamic LAG, the backup interface can be a static or dynamic LAG
In a redundant pair, any combination of physical and port-channel interfaces is supported as the two interfaces in a
redundant pair. For example, you can configure a static (without LACP) or dynamic (with LACP) port-channel interface
as either the primary or backup link in a redundant pair with a physical interface.
To ensure that existing network applications see no difference when a primary interface in a redundant pair transitions
to the backup interface, be sure to apply identical configurations of other traffic parameters to each interface.
If you remove an interface in a redundant link (remove the line card of a physical interface or delete a port channel with
the no interface port-channel command), the redundant pair configuration is also removed.
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