CCST Network Troubleshooting & Tools 5 — Questions and Answers
Question 1: A technician suspects a duplex mismatch between a PC and a switch port. Which command on a Cisco switch shows the current duplex setting of an interface?
- show ip interface brief
- show interfaces GigabitEthernet0/1 (Correct answer)
- show version
- show mac address-table
Correct answer: show interfaces GigabitEthernet0/1
The 'show interfaces' command for a specific port displays speed, duplex, and error counters that reveal duplex mismatches.
Question 2: What is the purpose of the 'ipconfig /release' command followed by 'ipconfig /renew' on a Windows PC?
- Flush the DNS cache and re-register the hostname
- Release the current DHCP lease and request a new IP address (Correct answer)
- Reset the TCP/IP stack to default settings
- Clear the ARP cache and rebuild MAC address mappings
Correct answer: Release the current DHCP lease and request a new IP address
'/release' surrenders the current DHCP-assigned IP address, and '/renew' sends a new DHCP discovery to obtain a fresh lease.
Question 3: Which tool is used to measure optical signal power levels in fiber optic cabling?
- Cable tester
- Optical power meter (Correct answer)
- TDR
- Multimeter
Correct answer: Optical power meter
An optical power meter measures the light signal strength in fiber optic cables, helping identify signal loss or insufficient power levels.
Question 4: A Cisco router shows 'up/down' for an interface. What does this indicate?
- The interface is administratively disabled
- The physical layer is active but the data link layer protocol has failed (Correct answer)
- The interface has correct IP configuration but no route
- The interface is fully operational
Correct answer: The physical layer is active but the data link layer protocol has failed
An 'up/down' state means the physical connection (Layer 1) is detected but the line protocol (Layer 2) has not established, often due to encapsulation or keepalive issues.
Question 5: Which command on Windows displays all active TCP and UDP connections along with the listening ports?
- ipconfig /all
- netstat -an (Correct answer)
- arp -a
- route print
Correct answer: netstat -an
The 'netstat -an' command shows all active network connections and listening ports in numerical format without DNS resolution.
Question 6: A technician is troubleshooting slow network performance and suspects excessive broadcasts. Which tool would BEST help quantify broadcast traffic on the segment?
- Cable tester
- Ping
- Protocol analyzer (Wireshark) (Correct answer)
- Nslookup
Correct answer: Protocol analyzer (Wireshark)
A protocol analyzer like Wireshark captures all traffic and can filter and count broadcast frames to determine whether excessive broadcasts are causing the performance issue.
Question 7: When troubleshooting a routing issue, a technician uses 'show ip route' and sees a route marked with 'C'. What does 'C' signify?
- A route learned via OSPF
- A directly connected network (Correct answer)
- A static route configured manually
- A route learned via BGP
Correct answer: A directly connected network
In Cisco IOS, the 'C' code in the routing table indicates a directly connected network — one that is on an interface configured with an IP address.
CCST Network Troubleshooting & Tools 5
A technician suspects a duplex mismatch between a PC and a switch port.
Which command on a Cisco switch shows the current duplex setting of an interface?