Ok, I think I am losing my mind here. I have a remote site that has some old 3500XL switches in the distribution and access layer. Distribution is 3508GXL with 1 link to the core and 6 to access switches. We needed to use the free port on the 3508G to trunk 6 vlans to one additional 3548XL. Ok, pretty straight forward right? Except that we can't get it to work. The native vlan (vlan 1) seems to forward, but none of the other vlans do. There is nothing funky about this config. ISL was used on the other trunks so we set this one up the same way. The only configuration statement on the Gig trunk on either side was "switchport mode trunk". I jerked it around a little when it didn't work just to see if I could figure out why. Changed it to a dot1q trunk, no joy. Added "switchport trunk pruning vlan none" just for grins, no luck.
A "show spanning" on both ends of the trunk shows that all Vlans are forwarding. BPDUs are being received by the 3548 on all Vlans. VTP domains are the same and the access switch receives VTP updates - pruning is disabled. "show mac-add vlan 50" on the 3548XL shows only the mac of adjacent switch, presumably the source mac of the BPDU's. I would expect to see macs for all the multicast traffic on that Vlan (mac aging is 14400).
What am I missing?