Spanning Tree Loop

[DANIEL MCKEEHAN]

I'm having a problem setting up an example redundant L2 configuration.  For reference I'm testing this in VIRL. 

What is happening is that the spanning tree is not properly blocking the spanning tree ports to prevent a loop.  I've tried enabling the bpdu guard feature and it just blocks all the ports.  The spanning tree keeps flapping on the ports.  This is using RSTP and the vlan in question is 999.   All switches below are NX-OSv.

I've attached all configs and the virl file, login is default admin/admin.

[marce1000]

 - The least of what you need in an initial spanning-tree setup is bpduguard. Use  defaulted settings as much as possible, for initial testing of spanning-tree convergence. Examine syslogs for more info. Make sure that there are no faulty connectors on any of the  links.

M.

[paul driver]

Hello

Have you specified an stp root switch for all vlans? - If not do so

remove any bpdu-filtering 

sh int trunk on each switch starting from the stp core which will have all trunks fwd/desg 

From there move to each switch and perform the same you should be able to T/S where the loop is originating from  it will be port that is for some reason forwarding when it shouldn’t be - the logging usually provides an indication  also to the root of the problem.

[AndiBuchmann157]

check the priorities and mac adresses of all devices, maybe something gets mixed up because of "simulator issues" and a proper election of the root bridge fails

[DANIEL MCKEEHAN]

One reply says to enable BPDU guard and another says not to.  From my understanding the STP should converge without BPDU and identify the loops in the listening phase.  I tried this in both GNS3 and in the VIRL networks and it fails in both.  I'm wondering if this is just a simulator issue.  I've seen other issues when attempting to test layer 2 configuration. 

Regarding the root switch Nexus-1 is forced primary for vlan 999 and Nexus-2 is forced to be the secondary.  

Show interface trunk doesn't yield any useful info. 

[paul driver]

Hello

Bpduguard should only be assigned on edge ports and not on any ports that you expect bpdus such as trunk ports

Bpdufilter filters bpdu thus effectively turning off spanning-tree thus is can cause switching loops if applied to the wrong ports trunk ports or access-posts

To manually specify a stp root switch

spanning-tree vlan 1,999 priority 0  < apply to primary core switch
spanning-tree vlan 1,999 priority 4096  <apply to secondary core switch