Software-Controlled Redundant Port and Smart Redundancy

Using the software-controlled redundant port feature, you can back up a specified Ethernet port (primary) with a redundant, dedicated Ethernet port. Both ports must be on the same switch.

If the primary port fails, the switch will establish a link on the redundant port and the redundant port becomes active. Only one side of the link must be configured as redundant because the redundant port link is held in standby state on both sides of the link. This feature provides very fast path or network redundancy.

Note

Note

You cannot have any Layer 2 protocols configured on any of the VLANs that are present on the ports.

The Smart Redundancy feature allows control over how the failover from a redundant port to the primary port is managed. If this feature is enabled, which is the default setting, the switch attempts to revert to the primary port as soon as it can be recovered. If the feature is disabled, the switch attempts only to recover the primary port to active if the redundant port fails.

A typical configuration of software-controlled redundant ports is a dual-homed implementation (shown in the following figure). This example maintains connectivity only if the link between switch A and switch B remains open; that link is outside the scope of the software-controlled port redundancy on switch C.

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Dual-Homed Implementation for Switch C
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In normal operation, the primary port is active and the software redundant switch (switch C in the following figure) blocks the redundant port for all traffic, thereby avoiding a loop in the network. If the switch detects that the primary port is down, the switch unblocks the redundant port and allows traffic to flow through that redundant port.

Note

Note

The primary and redundant ports must have identical VLAN membership.

You configure the software-controlled redundant port feature either to have the redundant link always physically up but logically blocked, or to have the link always physically down. The default value is to have the link physically down, or Off.

By default, Smart Redundancy is always enabled. If you enable Smart Redundancy, the switch automatically fails over to the redundant port and returns traffic to the primary port after connectivity is restored on that port. If you do not want the automatic restoration of the primary link when it becomes active, disable Smart Redundancy.