Finding interface IP and link status Which set of IOS commands will display an interface’s current IP addressing and its Layer 1/Layer 2 status information?

Difficulty: Easy

Correct Answer: 2, 3 and 5 (show protocols; show interfaces; show ip interface)

Explanation:


Introduction / Context:
Troubleshooting an IOS interface usually begins by confirming the IP address and the basic link state at Layer 1 (physical) and Layer 2 (data link). Multiple IOS commands expose these details from different angles. Knowing which commands provide what information helps you build a quick, repeatable triage flow.


Given Data / Assumptions:

  • The candidate commands are: show version; show protocols; show interfaces; show controllers; show ip interface.
  • We need to see IP addressing and link state (L1/L2).
  • Standard IOS behavior is assumed.


Concept / Approach:

show protocols lists the routed protocols and shows, per interface, whether they are up along with configured IP addresses. show interfaces provides comprehensive per-interface information including line status (up/down), protocol state, errors, and the interface's IP address. show ip interface summarizes IP-specific details (address, helper settings, ACLs) and includes interface status. In contrast, show version focuses on platform information and software, and show controllers provides low-level hardware/controller diagnostics without consistently listing IP addressing.



Step-by-Step Solution:

Use show protocols to confirm configured IP and basic up/down state.Use show interfaces to view L1/L2 status, errors, and the IP line in the output.Use show ip interface to confirm L3 details and operational status.Correlate the outputs to diagnose both addressing and link problems.


Verification / Alternative check:

Cross-checking across these three commands ensures accuracy: mismatches often reveal misconfigurations such as shutdown interfaces with IPs configured or ACLs blocking traffic despite link status being up.



Why Other Options Are Wrong:

  • Option A: show version does not list interface IPs; show controllers lacks full IP context.
  • Option C: omits show protocols or show ip interface, both of which help confirm IP addressing.
  • Option D: incorrect because a correct set exists.
  • Option E: show version again doesn't show interface IPs.


Common Pitfalls:

  • Using only one command and missing a key clue (for example, L1 up but L2 down).
  • Misreading cached outputs; always refresh with a new command invocation.


Final Answer:

2, 3 and 5 (show protocols; show interfaces; show ip interface)

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