Question

A network engineer configures 'spanning-tree guard root' on GigabitEthernet0/1 of a distribution switch, which connects to an access-layer switch managed by a different team. After the access switch's priority is lowered in an attempt to become the STP root, users on that segment lose connectivity. The 'show spanning-tree interface gi0/1 detail' output shows the port in a blocking state. What is the switch doing and how is connectivity restored?

Accepted Answer

Root guard placed the port in root-inconsistent state after receiving superior BPDUs; connectivity is restored automatically once the superior BPDUs stop arriving.

Answer

BPDU guard err-disabled the port after receiving a BPDU; the port must be manually re-enabled with 'shutdown/no shutdown'.

Answer

Loop guard placed the port in loop-inconsistent state after BPDUs stopped; connectivity returns only after a manual recovery timer expires.

Answer

The port entered broken state due to a native VLAN mismatch; connectivity is restored by aligning the native VLAN on both ends.