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Configure 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 configuring 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 configurations to each interface in the redundant pair such that their configurations are identical, so that
transition to the backup interface in the event of a failure is transparent to rest of the network.
Figure 73. 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.
Dell Networking OS 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
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