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Zorluk: KolayInterface and Cable Troubleshooting Issues

Match each Cisco IOS interface line status and line protocol state combination to its corresponding root cause.

  • GigabitEthernet0/1 is down, line protocol is downA Layer 1 physical issue exists, such as a disconnected cable, unpowered remote device, or bad pinout.
  • GigabitEthernet0/1 is administratively down, line protocol is downThe interface has been manually disabled using the 'shutdown' configuration command.
  • GigabitEthernet0/1 is up, line protocol is downA Layer 2 Data Link issue exists, such as a framing mismatch, keepalive failure, or clock rate issue.
  • GigabitEthernet0/1 is up, line protocol is up (disabled)The interface was disabled automatically by software features due to an operational error or port security violation.

Cevap

The interface states map to their corresponding root causes based on Layer 1 vs. Layer 2 status: down/down indicates a Layer 1 physical connectivity issue; administratively down indicates the port is shut down by configuration; up/down indicates a Layer 2 encapsulation or keepalive failure; and up/up (disabled) indicates an err-disabled state triggered by switch security features.
Matching interface states to their root causes requires analyzing Layer 1 and Layer 2 status lines: 'down/down' corresponds to a Layer 1 physical failure like an unplugged cable; 'administratively down' corresponds to an interface disabled by the 'shutdown' command; 'up/down' indicates Layer 1 is operational while Layer 2 framing or keepalives failed; and 'up/up (disabled)' corresponds to a port placed in the err-disabled state due to security or protocol violations.

Adım Adım Çözüm

1
Analyze 'down / down' interface output
Identified as a Layer 1 physical problem.
Lack of carrier signal or physical link pulse forces both the interface and protocol status to down.
2
Analyze 'administratively down / down' interface output
Identified as a software configuration shutdown state.
The 'shutdown' command explicitly disables the interface in software.
3
Analyze 'up / down' interface output
Identified as a Layer 2 Data Link problem.
Physical signal detection is successful ('up'), but protocol negotiation, keepalives, or encapsulation failed ('down').
4
Analyze 'up / up (disabled)' interface output
Identified as an error-disabled (err-disabled) port state.
Cisco IOS automatically disables active ports when severe error thresholds or port security limits are breached.

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Cisco IOS Interface Status and Line Protocol Troubleshooting
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