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question about RSTP

Hi !

I'm trying to understand RSPT and I had setup a small network lab with 4 Catalyst access switches. I provide a small schema of my lab setup. I wrote on the schema where I was expected and see root port, designated and alternated port.

But when I disconnect a topology change I see the topology converge very quickly. When I reconnect previously disconnected cables the spanning tree algorithm does not reconverge correctly and each tine I see 1 port place in error disable state…. I should each time reenable port manually to make spanning tree return to his original topology.

At the first time I was setup each connection with etherchannel configuration, because I was have some problems to my topology reconvergence after returning to originale state, I decide to connect one one cable in each etherchannel (avoiding problem with etherchannel it-self ) but same thing append…

Can someone help me ??

I'm a French people excuse my English !


Re: question about RSTP

you will probably have to post the configs . The err-disable part is probably a etherchannel problem where both sides of the channel do not have equal settings so the switch puts it in a err-disable state.

Community Member

Re: question about RSTP

here I attached the output of the following command :

sh run

sh cdp nei detail

sh int status

sh vers

Like I had tell in previous post only one ethernet cable on each etherchannel (make the etherchannel a virtual link contain only one physical connection) I was would like to removed etherchannel issues from my problems

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