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Spanning Tree and EtherChannel

greecemonkey
Level 1
Level 1

Hi,

I have four 3750s configured in 2 stacks of 2 devices.

Each device has two te ports and I have used ether channel to group the te ports.

This is a very basic question. When I disconnect a single te port spanning tree goes into

listening/ learning etc etc.

Maybe I have got it wrong, but why does spanning tree recycle if the port channel has not gone down.

All that has happened is one of the ports within the port channel has gone down.

How do I configure spanning tree to treat the port channel as the path and not the ports in the etherchannel

Graham

1 Reply 1

Hi Graham,

For the Background section," an EtherChannel is seen as a single port by STP. All the ports in the channel share the same STP state and only one STP bridge protocol data unit (BPDU) can be sent or received for each VLAN and for each hello interval.

This is not the case if one switch considers the links to be a channel and a neighbor switch considers those links to be separate connections."

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a008009448d.shtml

Please Check your Channel config.

E.g.

sh etherchan summ

Or your config..

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