CCST Network Troubleshooting & Tools 4 — Questions and Answers
Question 1: A technician needs to verify that TCP port 443 is open on a remote server. Which command can test this from a Windows command prompt?
- ping 10.0.0.1 -p 443
- telnet 10.0.0.1 443 (Correct answer)
- nslookup 10.0.0.1 443
- tracert 10.0.0.1 443
Correct answer: telnet 10.0.0.1 443
The telnet command followed by an IP and port number attempts a TCP connection to that specific port, confirming whether it is open.
Question 2: Which Cisco IOS command clears all dynamic entries from the ARP table?
- no arp
- clear arp-cache (Correct answer)
- delete arp table
- flush arp
Correct answer: clear arp-cache
The 'clear arp-cache' command removes all dynamically learned ARP entries from the Cisco device's ARP table.
Question 3: A network technician observes high CPU utilization on a Cisco router. Which command helps identify which processes are consuming CPU resources?
- show version
- show processes cpu (Correct answer)
- show memory
- show interfaces
Correct answer: show processes cpu
The 'show processes cpu' command displays CPU utilization per process, helping identify which process is causing high CPU load.
Question 4: What does a 'Destination host unreachable' ICMP message from ping indicate compared to 'Request timed out'?
- Both messages mean the same thing
- 'Destination host unreachable' means a router reported no route; 'Request timed out' means no reply was received (Correct answer)
- 'Request timed out' means a router reported no route; 'Destination host unreachable' means no reply was received
- Only 'Request timed out' indicates a routing problem
Correct answer: 'Destination host unreachable' means a router reported no route; 'Request timed out' means no reply was received
'Destination host unreachable' is an ICMP error returned by an intermediate router that has no route, while 'Request timed out' simply means the reply never arrived within the timeout.
Question 5: Which log level in Cisco IOS syslog captures the most detailed debugging information?
- Level 3 – Errors
- Level 5 – Notifications
- Level 7 – Debugging (Correct answer)
- Level 0 – Emergencies
Correct answer: Level 7 – Debugging
Syslog level 7 (debugging) is the most verbose level and captures all messages including detailed debugging output.
Question 6: A technician needs to confirm the MAC address of a remote host that is on the same subnet. Which command should be used after pinging the host?
- ipconfig /all
- arp -a (Correct answer)
- netstat -a
- route print
Correct answer: arp -a
After pinging a host on the same subnet, 'arp -a' shows the ARP cache which will contain the MAC-to-IP mapping for recently contacted hosts.
Question 7: Which troubleshooting approach starts at the Physical layer and works upward through the OSI model?
- Top-down
- Bottom-up (Correct answer)
- Divide-and-conquer
- Follow-the-path
Correct answer: Bottom-up
The bottom-up troubleshooting method begins at Layer 1 (Physical) and works up through each OSI layer until the problem is found.
CCST Network Troubleshooting & Tools 4
A technician needs to verify that TCP port 443 is open on a remote server.
Which command can test this from a Windows command prompt?