Verify Loopback0 Interface Status and Fast Switching Enabled

A

The correct command to verify the status of the Loopback0 interface and determine whether fast switching is enabled is:

C. Router#show interface loopback 0

Explanation:

• Option A (Router#show ip interface loopback 0) will display the IP configuration of the Loopback0 interface, but it won't provide information about fast switching.
• Option B (Router#show run) will display the running configuration of the router, which includes the configuration of the Loopback0 interface, but it won't provide information about the status of the interface or fast switching.
• Option D (Router#show ip interface brief) will display a brief summary of all interfaces, including their status and IP configuration, but it won't provide information about fast switching.

Therefore, option C is the correct command to use. This command will display detailed information about the Loopback0 interface, including its status, line protocol status, bandwidth, and whether fast switching is enabled or not. For example:

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Router#show interface loopback 0 Loopback0 is up, line protocol is up   Hardware is Loopback   Internet address is 10.0.0.1/32   MTU 1514 bytes, BW 8000000 Kbit/sec, DLY 5000 usec,      reliability 255/255, txload 1/255, rxload 1/255   Encapsulation LOOPBACK, loopback not set   Keepalive set (10 sec)   Fast switching enabled   ARP type: ARPA, ARP Timeout 04:00:00   Last input never, output never, output hang never   Last clearing of "show interface" counters never   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0   Queueing strategy: fifo   Output queue: 0/0 (size/max)   5 minute input rate 0 bits/sec, 0 packets/sec   5 minute output rate 0 bits/sec, 0 packets/sec      0 packets input, 0 bytes, 0 no buffer      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort      0 packets output, 0 bytes, 0 underruns      0 output errors, 0 collisions, 0 interface resets      0 unknown protocol drops      0 output buffer failures, 0 output buffers swapped out 

In the output, you can see that the Loopback0 interface is up and the line protocol is up, indicating that the interface is operational. Additionally, the "Fast switching enabled" line indicates that fast switching is enabled for the interface.