ICND1 Troubleshooting 2

Question 1

A router shows 'Serial0/0 is down, line protocol is down.' What is the FIRST step to troubleshoot this issue?

Accepted Answer

Check the physical cable and CSU/DSU

Answer

A down/down state indicates a Layer 1 physical problem, so checking the cable and CSU/DSU is the appropriate first step.

Question 2

Which command would you use to verify that CDP neighbors are being detected on a Cisco switch?

Accepted Answer

show cdp neighbors

Answer

'show cdp neighbors' displays directly connected Cisco devices discovered via the Cisco Discovery Protocol.

Question 3

A host can ping its default gateway but cannot reach remote networks. What should you check on the router?

Accepted Answer

Routing table on the router

Answer

If the gateway is reachable but remote networks are not, the router's routing table likely lacks the necessary routes.

Question 4

The output of 'show interface FastEthernet0/0' shows 'input errors' incrementing. What does this most likely indicate?

Accepted Answer

Duplex mismatch or bad cable causing CRC errors

Answer

Input errors, especially CRC errors, are commonly caused by duplex mismatches or physical layer problems like damaged cables.

Question 5

You issue 'ping 10.1.1.1' from a router and receive 'U.U.U.' in the output. What do the 'U' characters indicate?

Accepted Answer

The destination is unreachable

Answer

A 'U' in ping output represents an ICMP Destination Unreachable message received back from a router.

(ICND1) Interconnecting Cisco Networking Devices Part 1 Practice Test