Hi Guys,
I am trying to reproduce a Spanning-Tree loop in my lab that occurred on Ops, and for the life of me I cannot break it. The loop is very simple:
On Ops:
Cisco 2960------------FW that doesn't forward STP traffic-----------Cisco 2960
| |
|-------------------------------------------------------------------------------------------|
This created an STP loop. In my lab, I am substituting the FW for another Cisco 2960 with STP disabled and BPDUFilter on ingress/egress ports to stop the switch from sending BPDU's to the downstream switch to keep it in the dark, as the FW did on Ops.
Stand-in SW 4 FW#show spanning-tree
No spanning tree instance exists.
Stand-in SW 4 FW#show run | begin interface FastEthernet0/23
interface FastEthernet0/23
spanning-tree bpdufilter enable
interface FastEthernet0/24
spanning-tree bpdufilter enable
Now, to my knowledge, I've just stopped the stand-in FW switch from sending and recieving BPDU's; emulating the Ops Firewall, so my downstream switch should assume it is safe to bring up the loop, since it's not recieving BPDUs. However, every time I plug in the loop, STP still blocks it.
How can this be if I've cut off the BPDU supply to the downstream switch?
