- Bronze, 100 points or more
Topology - 6500s at the Core, connected by 20 GB EtherChannel. 2950s at the access layer, all connected to the core via 2 GB EtherChannels. The cores have about 80 VLANs, and each access switch has between 5-10 (VTP is not used). All switches run Rapid PVST.
What we've observed in a few cases is that the access switches don't receive BPDUs from one (or both) or the Core Switches, but only for certain VLANs. These VLANs are allowed in the Trunk (EtherChannels) on both the access and Core side.
We have noticed the root bridge configuration for these VLANs was a bit off, because one of the server distribution switches was configured as root. However, under RSTP, all bridges should be sending BPDUs, so that still doesn't explain the behavior.
We're working with TAC, but this has been a head-scratcher and wonder if anyone else had encountered anything like this. Loopguard is enabled on the cores, but not the access switches, so we don't know exactly when the problem started.