A loop was created betweeen switch A and switch B and this caused the entire netowrk to go down. Both switches had STP enabled and switch A was the root. Switch A and switch B were connected via one copper port on each switch. What I found was that switch B was configured with the interconnect port in a trunk, and switch A was not.
example
- switch A:
- vlan 1
- untagged 48
- switch B:
- trunk trk1 eth 48
- vlan 1
- untagged trk1
the loop was introduced between switch A and B on some other ports, say 5 and 6 which are configured as access ports but the loop was not detected. Anyone know why this misconfiguration between the interconnect ports would cause this failure?