Fast Uplink Span Rules for LAGs

If you add a port to a Fast Uplink Span group that is a member of a LAG, the following rules apply:

• If you add the LAG virtual interface of a LAG to the Fast Uplink Span group, all other ports in the LAG are automatically included in the group. Similarly, if you remove the LAG virtual interface from the Fast Uplink Span group, the other ports in the LAG are automatically removed from the Fast Uplink Span group.
• You cannot add a subset of the ports in a LAG to the Fast Uplink Span group. All ports in a LAG have the same Fast Uplink Span property, as they do for other port properties.
• If the working LAG is partially down but not completely down, no switch-over to the backup occurs. This behavior is the same as in the standard STP feature.
• If the working LAG is completely down, a backup LAG can go through an accelerated transition only if the following are true:
  • The LAG is included in the fast uplink group.
  • All other ports except those in this LAG are either disabled or blocked. The accelerated transition applies to all ports in this LAG.

When the original working LAG comes back (partially or fully), the transition back to the original topology is accelerated if the conditions listed above are met.