NE NE Network Troubleshooting 1 — Questions and Answers
Question 1: What is the correct order of the OSI model troubleshooting approach when using a bottom-up method?
- Application → Transport → Network → Data Link → Physical
- Physical → Data Link → Network → Transport → Application (Correct answer)
- Network → Physical → Application → Transport → Data Link
- Transport → Network → Data Link → Physical → Application
Correct answer: Physical → Data Link → Network → Transport → Application
Bottom-up troubleshooting starts at Layer 1 (Physical) and works up, verifying each layer before moving to the next, ensuring foundational issues are not missed.
Question 2: Which command verifies end-to-end IP reachability between two hosts?
- traceroute
- ping (Correct answer)
- netstat
- ipconfig
Correct answer: ping
Ping sends ICMP Echo Request packets to a destination and reports whether responses are received, confirming IP-layer reachability.
Question 3: What does a high number of CRC errors on a switch interface typically indicate?
- A routing loop in the network
- Physical layer issues such as bad cable, duplex mismatch, or faulty NIC (Correct answer)
- An overloaded routing table
- An incorrect VLAN assignment
Correct answer: Physical layer issues such as bad cable, duplex mismatch, or faulty NIC
CRC errors indicate corrupted frames, most commonly caused by physical problems: damaged cables, duplex mismatches, or faulty hardware.
Question 4: A user cannot access a remote server but can ping the default gateway. What is the most likely issue?
- The user's NIC is faulty
- Routing or firewall issue between the user's network and the server's network (Correct answer)
- The user has an incorrect subnet mask
- The switch port is in the wrong VLAN
Correct answer: Routing or firewall issue between the user's network and the server's network
If the gateway is reachable but the remote server is not, the problem lies beyond the local network — in routing, ACLs, or firewall rules in the path.
Question 5: What tool is used to identify the path packets take from a source to a destination and detect where delays occur?
- ping
- nslookup
- traceroute / tracert (Correct answer)
- netstat
Correct answer: traceroute / tracert
Traceroute (tracert on Windows) sends packets with increasing TTL values to discover each hop in the path and measure round-trip time at each hop.
Question 6: A duplex mismatch between a switch port and a connected device will cause which symptom?
- Complete loss of connectivity
- High number of late collisions and poor throughput (Correct answer)
- Increased broadcast traffic
- VLAN membership errors
Correct answer: High number of late collisions and poor throughput
A duplex mismatch (one side full-duplex, other half-duplex) causes late collisions on the half-duplex side and reduced throughput without complete link failure.
NE NE Network Troubleshooting 1
What is the correct order of the OSI model troubleshooting approach when using a bottom-up method?