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Possible STP Issue

Occasional Contributor

Possible STP Issue

Hello I am currently working on provisioning a wired network for a new building. Below I have a quick illustration of my issue. Please note that the topolgy that Ive illustrated is set up for specific reasons. I am merely looking to address a possible stp issue. The top Topology is the one Im attempting to make work, but for some reason it just decides not to work. I have provisioned all switches with just basic setup informations (Security, STP is on, IP information). When my copper line from my MDF is plugged into the second switch at the MDF, then I am only able to access that one switch. However, If I unplug that switch at the MDF and plug the IDF switch in then it works. I have rolled through all of the "Show Spanning-Tree" "Show Tech Stat" and "Show Spanning-Tree Debug-Counters Ports All Instances 0" Commands looking for anything odd, but I am not seeing anything that would cause this. One last note is that when I attempt it the first way, The Fibre Ports show active and appear to be active. Issue.jpeg

Esteemed Contributor

Re: Possible STP Issue

Hi Dcoy05,


Including a copy of the "show spanning-tree" output from each switch in each configuration would shed a lot more light on this problem.

Trusted Contributor

Re: Possible STP Issue

The topology you are trying to setup doesn't appear to include any loop - unless the links you have drawn represent multiple parallel paths.

If the former applies, then it's probably either a connectivity problem (does the inter-switch link at the MDF get a link? Does show LLDP work?) or it's a VLAN trunking problem.


If the latter applies, then, as Paul says, check your spanning-tree (what state is it in on each switch? Are the MDF switches configured with lower priorities and Is the "Core" configured with a lower priority than all the others?).