Match each switch status indicator or log message on the left with its corresponding underlying root cause on the right.
- %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/1 (10), with Switch2 GigabitEthernet0/1 (20).Untagged frames are arriving on a trunk interface whose default 802.1Q VLAN ID does not match the adjacent switch.
- Interface FastEthernet0/12 reports an increasing counter for CRC errors and late collisions during heavy traffic.Duplex misconfiguration where one port is manually set to full-duplex while the connecting port defaults to half-duplex.
- Interface GigabitEthernet0/2 transitions to err-disabled state after receiving BPDUs with a bridge priority of 0.STP Root Guard protection triggered by receiving a superior Bridge Protocol Data Unit on an interface designated for downstream access.
- Trunk port operational state is up, but frames belonging to VLAN 30 are dropped while VLAN 10 frames pass normally.Trunk interface configuration contains an explicit allowed VLAN list that excludes VLAN 30 from traversing the link.
Answer
Each switch indicator matches its root cause: Native VLAN mismatch log matches untagged frame default VLAN mismatch; CRC errors and late collisions match duplex misconfiguration; Err-disabled port from priority 0 BPDU matches STP Root Guard enforcement; Trunk passing VLAN 10 but dropping VLAN 30 matches trunk allowed VLAN list exclusion.
Each indicator corresponds to a classic Layer 2 troubleshooting symptom: CDP log warnings indicate non-matching native VLAN IDs on 802.1Q trunks; late collisions with CRC errors indicate a full-duplex/half-duplex mismatch; an err-disabled state after receiving a priority 0 BPDU indicates STP Root Guard action; and selective VLAN dropping on an active trunk indicates an incomplete allowed VLAN list.
Step-by-Step Solution
Key Concept
Switching and VLAN Troubleshooting Indicators