Users Guide

Congure Redundant Pairs
Networks that employ switches that do not support the spanning tree protocol (STP) — for example, networks with digital
subscriber line access multiplexers (DSLAM) — cannot have redundant links between switches because they create switching loops
(as shown in the following illustration).
The redundant pairs feature allows you to create redundant links in networks that do not use STP by conguring backup interfaces
for the interfaces on either side of the primary link.
NOTE: For more information about STP, refer to Spanning Tree Protocol (STP).
Assign a backup interface to an interface using the switchport backup command. The backup interface remains in a Down
state until the primary fails, at which point it transitions to Up state. If the primary interface fails, and later comes up, it becomes the
backup interface for the redundant pair. Dell Networking OS supports Gigabit, 10 Gigabit, and 40-Gigabit interfaces as backup
interfaces.
Apply all other congurations to each interface in the redundant pair such that their congurations are identical, so that transition to
the backup interface in the event of a failure is transparent to rest of the network.
Figure 74. Conguring Redundant Layer 2 Pairs without Spanning Tree
You congure 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 trac 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.
Layer 2
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