Connection to 3Com switch blocked due to BPDU

[gordon.ross]

I've got a 3Com 2226 switch. It has a trunk connection uplink to another switch (Actually a Cat 6509). I've connected an 877 router to one of the normal, non-trunk, ports on the switch.

Whenever I plug in the router, I get:

*Mar 1 00:18:01.679: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0 VLAN1.

*Mar 1 00:18:01.679: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0 on VLAN1. Inconsistent port type.PVST+: restarted the forward delay timer for FastEthernet0

Either I'm doing something wrong on the 3Com switch, or doing something wrong on the 877 router. (At this stage the router has no config apart from an IP address on VLAN1) Can anyone point me in the right direction ?

Thanks,

GTG

[Kevin Dorrell]

Do I understand correctly that these messages appear on the router (i.e. not the 6509)? I think that is the case.

So I reckon the 3Com switch is passing the PVST+ BPDUs through, simply because it does not understand them.

One thing you could do is put bpdu-filter on the 6509 port facing the 3Com. But be very very careful that you never, ever, risk a loop based on the 3Com, because Spanning Tree will not protect you against that any more.

Or replace the 3Com with a Cisco PVST+ aware switch.

Kevin Dorrell

Luxembourg