CCST Network Troubleshooting & Tools 3 — Questions and Answers
Question 1: A technician runs 'nslookup cisco.com' and receives a 'Non-existent domain' error. What is the MOST likely cause?
- The website is down
- The DNS server cannot resolve the name (Correct answer)
- The default gateway is incorrect
- The NIC driver is corrupted
Correct 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.
Question 2: Which command on a Cisco router shows whether OSPF neighbor adjacencies have formed?
- show ip ospf database
- show ip ospf neighbor (Correct answer)
- show ip route ospf
- debug ip ospf events
Correct answer: show ip ospf neighbor
The 'show ip ospf neighbor' command lists all OSPF neighbors and their current state, confirming whether adjacencies are established.
Question 3: A user's computer shows 'Limited connectivity' and has an IP address of 169.254.x.x. What does this indicate?
- The user has a static IP configured
- DHCP failed and the host assigned itself an APIPA address (Correct answer)
- The subnet mask is incorrect
- DNS is unreachable
Correct 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.
Question 4: When using Wireshark, which filter would display only HTTP traffic?
- port 80
- tcp.port == 80
- http (Correct answer)
- protocol == http
Correct answer: http
In Wireshark's display filter, typing 'http' filters the capture to show only packets identified as HTTP protocol.
Question 5: A switch port is in 'err-disabled' state. What is the FIRST step to recover it?
- Replace the switch
- Identify the cause, fix it, then shut/no shut the interface (Correct answer)
- Reboot the switch
- Change the VLAN on the port
Correct 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.
Question 6: Which command verifies Layer 3 connectivity between two Cisco devices while also showing the path?
- ping
- traceroute (Correct answer)
- show ip route
- telnet
Correct answer: traceroute
The traceroute command tests Layer 3 connectivity and reveals each hop along the path to the destination.
Question 7: A cable is suspected of being faulty. Which physical layer tool can test cable continuity and pair mapping?
- Protocol analyzer
- Cable tester (Correct answer)
- OTDR
- Spectrum analyzer
Correct answer: Cable tester
A cable tester checks for continuity, correct pair mapping, shorts, and opens in copper Ethernet cables.
CCST Network Troubleshooting & Tools 3
A technician runs 'nslookup cisco.com' and receives a 'Non-existent domain' error.
What is the MOST likely cause?