enabling spanning tree

[vishalpatil86]

Hi,

kindly explain eaning of below -

when i assign a port to a vlan and enable spanning tree portfast feature, i get following message -

sw#spanning-tree portfast

%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

%Portfast will be configured in 10 interfaces due to the range command

but will only have effect when the interfaces are in a non-trunking mode.

[Jon Marshall]

First warning is standard warning about where to apply portfast ie. don't apply it on uplinks to switches is pretty much what it is saying.

2nd warning is presumably because you are configuring a range of interfaces and not just one.

Jon

[Ven Taylor]

Jon is absolutely correct.  Informational output only.

[vishalpatil86]

hi,

thanx for the reply.

But what is the meaning of following line -

but will only have effect when the interfaces are in a non-trunking mode.

interface is already in non-trunking mode.

This is also informational?

[Jon Marshall · Accepted solution]

Yes it is informational only. If you want to apply portfast to a trunk link there is a separate command -

spanning-tree portfast trunk

although note that this should still not be applied to switch uplinks. The portfast trunk command is mainly used when you have a server running a trunk link connected to the switch.

Jon

[vishalpatil86]

got it jon.

thanx