N10-009 Question 305
Single answerPort status: Error disabled, Administratively down, SuspendedA network technician is troubleshooting user connectivity after replacing a desk phone and reconnecting the attached PC to an access switch. The switch shows three different interface states on various ports: Gi1/0/10 is "err-disabled," Gi1/0/11 is "administratively down," and Gi1/0/12 is "suspended." The technician needs to identify which port most likely requires a configuration change to bring it up because it was intentionally shut down by an administrator, rather than blocked by a protocol or disabled because of a fault. Which port should the technician investigate first?
- A
Gi1/0/10, because an err-disabled port indicates the interface was manually shut down for maintenance
- B
Gi1/0/11, because administratively down indicates the interface is in a shutdown state in the configuration
- C
Gi1/0/12, because suspended indicates the interface is physically disconnected and waiting for link
- D
Any of the three ports, because these states all mean the same thing and require only a cable replacement
Show answer and explanation
Correct answer: B
Explanation
The best answer is Gi1/0/11 because administratively down is the status most clearly associated with an interface that has been intentionally disabled in the configuration. On Cisco-style switches and in common networking practice, this is typically caused by the shutdown command and is reversed with no shutdown. By contrast, err-disabled is a protective state entered automatically after specific events such as port-security violations, BPDU Guard triggers, UDLD issues, or other platform-specific fault conditions. Suspended is commonly seen when a switch intentionally prevents an interface from forwarding due to an inconsistency, often involving EtherChannel or similar logical link conditions. Best practice is to use interface status commands and review logs to determine whether a port was shut down manually, disabled by a protection mechanism, or suspended by a protocol. Vendor documentation for interface states and operational status outputs supports these distinctions.
- A. Incorrect.
Incorrect. An err-disabled port is typically placed into a disabled state automatically by the switch after a fault or policy violation, such as port security violations, BPDU Guard, or link-flap detection, depending on platform and configuration. It is not the same as a port intentionally shut down by an administrator. A candidate might choose this if they confuse a disabled state with a manual shutdown.
- B. Correct.
Correct. Administratively down means the interface has been disabled in the running or startup configuration, usually with the shutdown command. This is the state most directly associated with an intentional administrative action, and bringing it back up generally requires a configuration change such as no shutdown.
- C. Incorrect.
Incorrect. Suspended does not mean the port is simply unplugged. In switching environments, suspended commonly indicates the port has been logically prevented from forwarding because of a control-plane or aggregation issue, such as an EtherChannel inconsistency or related protocol condition. Someone might choose this if they confuse logical suspension with a lack of physical carrier.
- D. Incorrect.
Incorrect. These states do not mean the same thing. Administratively down points to a manual shutdown, err-disabled usually indicates an automatic protective disablement due to a detected problem, and suspended typically indicates a protocol or bundling-related condition. Replacing a cable would not resolve all of these states and may not resolve any of them.