How to enable loop guard for a trunk port when ....?

[astanislaus]

Loop guard should only be enabled on non-designated (i.e. root ports and blocked ports). Loop guard should not be enabled on designated ports - Correct ? Right.

So:

How to enable loop guard on a trunk port where the port is designated for some VLANs and non-designated for other VLANs. There are a few articles on CCO trying to explain this, but I am yet to find one that I can understand.

Can this be done or can't this be done?

alphonse.stanislaus@hp.com

[mchin345]

The loop guard is enabled on a per-port basis. However, as long as it blocks the port on the STP level, it blocks inconsistent ports on a per-VLAN basis (because of per-VLAN STP). That is, if on the trunk port, BPDUs are not received for only one particular VLAN, only that VLAN will be blocked (moved to loop-inconsistent STP state). For the same reason, if enabled on an EtherChannel interface, the entire channel will be blocked for a particular VLAN, not just one link (because EtherChannel is regarded as one logical port from STP point of view).

http://www.cisco.com/warp/public/473/84.html