Multiple choice

Refer to the exhibit. Router R1 is not able to communicate with a neighbour router that is directly connected to serial 0/0/0. What is the reason for this?

  1. Interface Serial0/0/0 resets very frequently.

  2. PPP LQM has shutdown the serial interface.

  3. The serial interface has no input or output queues available.

  4. The serial interface is not configured for a Layer 2 protocol.

  5. The interface has been administratively shutdown with the shutdown command.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The serial interface cannot communicate because no Layer 2 protocol (like PPP, HDLC, or Frame Relay) has been configured. Serial interfaces require explicit Layer 2 encapsulation configuration to function. The other options are incorrect: interface resets (A) wouldn't prevent communication, LQM (B) is a specific PPP feature not relevant here, missing queues (C) is not the issue, and the interface is not administratively shutdown (E) as evidenced by 'up/down' or similar state.

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