I have an strange problem and a question regarding VLAN trunking, as well as some queries regrading spanning tree.
Strange VLAN trunking problem:
I'm trying to apply "switch port trunk allow vlan <x,y,z>" statements to two uplinks from an access layer 3 3750 stack, to two distribution layer 3 6509's. Originally each link was configured as an access link. I''ve converted the link to trunk and applied the relevant "allow" statement to both of the access layer trunk uplink ports.
When I apply the relevant "allow" statement to the distribution switch trunk ports, instead of simply seeing the relevant allowed VLAN's, and being then able to simply ping from one neighbour (dist to access) to the other, as well as see from traceroute a neighbour being the next hop away, instead the ping from each neighbour to the other does not work and times out, nor does traceroute.
The links now have "switch port trunk allow vlan <x,y,z>" on the access layer uplink ports, but none on the distribution pots. The links appear to work as trunk links (ping and tracerouter are ok), however from the access layer the trunk allows through only the allowed VLAN's , but from the distribution ports all of the VLAN's appear to be allowed through. Any thoughts on what has gone wrong here and how do i fix it ??
Spanning Tree query.
Is there a need for spanning tree (in this case pvst+) in a trunked fully switched layer 3 access, distribution, core environment. If so what is the effect of blocked ports on routing updates ?
Your help woould be appreciated