Match each switch log message or port status indicator on the left with its corresponding root cause on the right.
- %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/1 (10), with Switch-B GigabitEthernet0/1 (20).Mismatched untagged VLAN IDs configured on opposing trunk interface endpoints
- Interface GigabitEthernet0/2 status shows increasing late collisions and FCS frame check sequence errors under high load.Duplex mismatch caused by hardcoding one end to full-duplex while auto-negotiation fails on the other
- %SPAN-4-PORT_BLOCKING: Port GigabitEthernet0/24 blocked by Spanning Tree Protocol due to receiving a superior BPDU.STP root bridge priority misconfiguration or introduction of a rogue switch with a lower priority value
- Access port FastEthernet0/5 is assigned to VLAN 40, but connected hosts cannot communicate and show interface down/line protocol down (inactive VLAN).Missing VLAN entry in the switch local VLAN database (vlan.dat)
Answer
The CDP native VLAN mismatch log corresponds to mismatched untagged VLAN IDs across a trunk link. Increasing late collisions and FCS errors correspond to a duplex mismatch between connected interfaces. The STP superior BPDU blocked port log corresponds to an unexpected switch advertising a lower STP priority. The inactive access port condition corresponds to a missing VLAN definition in the local switch VLAN database.
Each switch log or status symptom maps directly to a distinct Layer 2 misconfiguration: CDP warning logs pinpoint native VLAN mismatches, late collisions indicate duplex mismatches, superior BPDU logs indicate STP priority conflicts, and inactive port assignments indicate uncreated local VLANs.
Step-by-Step Solution
Key Concept
Troubleshooting Layer 2 switching issues including native VLAN mismatches, duplex misconfigurations, STP topology dynamics, and missing VLAN database entries.