Network Troubleshooting & Tools Flashcards

A technician runs 'nslookup cisco.com' and receives a 'Non-existent domain' error. What is the MOST likely cause?

Answer: The DNS server cannot resolve the name

A 'Non-existent domain' (NXDOMAIN) response from nslookup means the DNS server responded but could not find a record for that name.

Which command on a Cisco router shows whether OSPF neighbor adjacencies have formed?

Answer: show ip ospf neighbor

The 'show ip ospf neighbor' command lists all OSPF neighbors and their current state, confirming whether adjacencies are established.

A user's computer shows 'Limited connectivity' and has an IP address of 169.254.x.x. What does this indicate?

Answer: DHCP failed and the host assigned itself an APIPA address

A 169.254.x.x address is an APIPA (Automatic Private IP Addressing) address assigned when a DHCP server cannot be reached.

When using Wireshark, which filter would display only HTTP traffic?

Answer: http

In Wireshark's display filter, typing 'http' filters the capture to show only packets identified as HTTP protocol.

A switch port is in 'err-disabled' state. What is the FIRST step to recover it?

Answer: Identify the cause, fix it, then shut/no shut the interface

You must first identify and fix the root cause of the error (such as a loop or security violation), then use 'shutdown' followed by 'no shutdown' to restore the port.

Which command verifies Layer 3 connectivity between two Cisco devices while also showing the path?

Answer: traceroute

The traceroute command tests Layer 3 connectivity and reveals each hop along the path to the destination.

A cable is suspected of being faulty. Which physical layer tool can test cable continuity and pair mapping?

Answer: Cable tester

A cable tester checks for continuity, correct pair mapping, shorts, and opens in copper Ethernet cables.