Software-controlled redundant ports and port groups have the following guidelines and limitations:
You cannot have any Layer 2 protocols configured on any of the VLANs that are present on the ports. (You will see an error message if you attempt to configure software redundant ports on ports with VLANs running Layer 2 protocols.)
The primary and redundant ports must have identical VLAN membership.
The master port is the only port of a load-sharing group that can be configured as either a primary or redundant port. Also, all ports on the load-sharing group must fail before the software-controlled redundancy is triggered.
You must disable the software redundancy on the master port before enabling or disabling load sharing.
You can configure only one redundant port for each primary port.
Recovery may be limited by FDB aging on the neighboring switch for unidirectional traffic. For bi-directional traffic, the recovery is immediate.