Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Spanning tree - what would happen if ?

Hi there

If I had 2 distribution switches, then an access layer switch dual homed to both dist switches, running STP, But if I effectivley turned off STP on the link between the dist switches, what would happen on the access switch ? would it still work and block as per normal ?

6 REPLIES
Hall of Fame Super Silver

Re: Spanning tree - what would happen if ?

Hello Carl,

>> But if I effectivley turned off STP on the link between the dist switches,

do it only if between the two distribution switches there is a L3 path otherwise you are in trouble.

Hope to help

Giuseppe

Purple

Re: Spanning tree - what would happen if ?

You would then likely not have anything blocking on the access layer as you have eliminated the inherent loop in the network.No different than say having 2 uplinks and then a routed crosslink .

New Member

Re: Spanning tree - what would happen if ?

hi there

thanks for that, one more question, can you still use HSRP on the dist routers for the access layer clients if there is a layer 3 link between them ?

Purple

Re: Spanning tree - what would happen if ?

Sure , not a problem .

New Member

Re: Spanning tree - what would happen if ?

Hi Glen

Does this mean that all the hsrp traffic will be flowing through the access to dist uplinks?

New Member

Re: Spanning tree - what would happen if ?

Correct - you need a layer 2 link between the two SVIs participating in HSRP, so the HSRP hellos would be flowing through the access switch to maintain adjacency.

I have never deployed this type of design, we tend to stick with the traditional looped topology between access and distribution, using Rapid-PVST+ to maintain a loop free topology.

If you have many access switches using the same Vlan you may start to complicate design / troubleshooting by removing the layer 2 link between the distribution switches.

126
Views
5
Helpful
6
Replies
CreatePlease to create content