This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

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Friday, April 30, 2010

Question 60

Can you use portfast on a trunk?

2 comments:

Unknown said...

Yes. Cisco is even kind enough to provide you with a warning...

Switch(config)#interface fastethernet 0/1
Switch(config-if)#spanning-tree portfast trunk
%Warning: portfast should only be enabled on ports connected to a single host. Connecting hubs, concentrators, switches, bridges, etc… to this interface when portfast is enabled, can cause temporary bridging loops.
Use with CAUTION

Packets Analyzed said...

As indicated in the warning when using portfast on a trunk you must ensure that you do not have multiple links to the switch or you will create a bridging/spanning-tree loop

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