A network technician is troubleshooting interface and cabling symptoms across enterprise switches. Match each Cisco IOS interface status output or error counter on the left with its most probable root cause on the right.
- Interface output displays 'GigabitEthernet0/1 is down, line protocol is down'.Physical Layer (Layer 1) failure such as a disconnected cable or unpowered remote device.
- Interface output displays 'FastEthernet0/2 is up, line protocol is down'.Data Link Layer (Layer 2) issue such as a keepalive failure or framing mismatch.
- Interface statistics show an increasing counter of Late Collisions.Duplex mismatch between the local switch port and the connected device.
- Interface statistics show high CRC and Input Errors without collisions.Physical media impairment, damaged pin connector, or electromagnetic interference.
Answer
Match 'down/down' to Layer 1 physical failure; 'up/down' to Layer 2 data link issue; 'Late Collisions' to duplex mismatch; and 'CRC errors' to physical media impairment or electromagnetic interference.
Each status combination and error counter directly corresponds to its underlying network layer or physical cabling cause. An interface status of 'down/down' reflects Layer 1 physical disconnection. An interface status of 'up/down' indicates Layer 2 data link failure. Late collisions indicate a duplex configuration mismatch. CRC errors without collisions indicate physical frame corruption due to cable degradation or electrical interference.
Step-by-Step Solution
Key Concept
Cisco IOS Interface Status and Troubleshooting Error Counters