Dell S4820T, Configuration Manual

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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 69. Configuring Redundant Layer 2 Pairs without Spanning Tree
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Layer 2