CompTIA Network+ (N10-009)Network TroubleshootingMedium
A technician is using the `ping` command to troubleshoot connectivity to a remote server. The command output shows `Destination Host Unreachable` messages. The technician then runs `traceroute` to the same destination and observes that the output stops at the first hop (the local router). Which of the following is the MOST likely cause of this issue?
- ADNS resolution for the remote server is failing.
- BThe default gateway on the technician's workstation is incorrect.
- CA firewall on the remote server is blocking ICMP.
- DThe remote server is offline.
Show answer & explanationAnswer & explanation
Correct answer: B. The default gateway on the technician's workstation is incorrect.
If `ping` returns `Destination Host Unreachable` and `traceroute` stops at the first hop (the local router), it indicates that the workstation cannot even successfully send traffic beyond its local network to reach the router. This is a classic symptom of an incorrect default gateway configuration on the workstation, as it doesn't know where to send traffic for destinations outside its local subnet.
Why the other options are wrong
- A. DNS resolution failure would prevent communication by hostname, but the question implies pinging an IP or a hostname and getting a 'host unreachable' message, which is a routing issue, not a name resolution issue.
- C. A firewall blocking ICMP on the remote server would cause `ping` to time out at the destination, but `traceroute` would still show successful hops to intermediate routers.
- D. If the remote server were offline, `ping` might time out, but `traceroute` would typically progress past the first hop, reaching intermediate routers before failing.
Incorrect Default Gateway
A misconfigured IP address that tells a device where to send traffic destined for networks outside its local subnet.
- Prevents communication with any external networks.
- Symptoms: 'Destination Host Unreachable' for external IPs, `traceroute` failing at first hop.
- Verify by checking IP configuration on the client device.
Memory trick: Can't leave the block? Check the 'exit ramp' (gateway).