Cat 6509 does not send BPDU

[yangfei]

Hello there,

I have 2 Cisco 6509, running Cat OS, as the core switches. Cisco 3548 and 4000 series switches are the distribution layer, connected to the two 6509 via fiber Gigabit interface. One 6509 is the root bridge for all VLANs. All VLANs configurations are same on the 6509-1. STP timers are kept as default for all switches.

The problem is that all VLANs work fine, except VLAN48. In VLAN 48, the 6509 does not send BPDU out, though it is the root bridge for VLAN 48. I confirmed this by using sniffer and "show spanning-tree statistics" command on 6509, no BPDU captured every 2 seconds. So, after 20 seconds, the 3548 and 400 switches broadcast BPDU claiming that they are the root bridge. As soon as these switches send out BPDU, the root bridge, 6509, sends out its BPDU, announcing that it is the root. Since 6509 has the lowest bridge priority, all other switches accept that it is the root. But, after this, 6509 does not send any more BPDU. So, after another 20 seconds, all 3548 and 4000 switches start sending BPDU again....

When I use ethereal in other VLANs, I can capture BPDUs sent from the 6509 every 2 seconds.

All the configurations for VLANs are same, but only VLAN 48 gets the problem.

I wonder if you have any suggestions for this.

Thanks in advance,

Fei.

[vmoopeung]

This is a strange behavior, Could you be more specfic about the Version you are using in the switchs . Have you enabled pruning for this Vlan.

[skarundi]

yes i agree this is a strange problem. probably requires detailed hardware programming troubleshooting to understand the state of vlan 48 on the core switch.

If you have a Cisco contract open a TAC case.

pruning only blocks data from been sent out using a particular vlan. doesn't block BPDUs.

have you considered not using vlan 48 and using another vlan instead since all the vlans work fine ? Just delete vlan 48 from your switches' database and use another vlan.