Dears,
user takes a network cable and plugs it into two wall jacks, this creates a loop, a broadcast storm will likely follow. This happened to us by having an end user hooking up their IP phone to two network jacks. It brought down the entire network.
and
- BPDU GUARD enabled globally
- BPDU filter not enabled
- port fast enabled under access ports
switch C3750 connected to core c9500
logs
STP-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV
Thanks to share the solution for this issue