ISC2 Certified in Cybersecurity (CC)Network SecurityMedium
A network engineer is troubleshooting a connectivity issue where a new server cannot reach resources on a different subnet, even though its IP address, subnet mask, and gateway are correctly configured. The server's firewall is temporarily disabled for testing. Other devices on the same subnet can reach the remote resources. What is the MOST likely cause of the problem?
- AIncorrect DNS server configuration on the server.
- BA missing or incorrect route entry on the network router.
- CThe server's network adapter drivers are outdated.
- DA broadcast storm is occurring on the local subnet.
Show answer & explanationAnswer & explanation
Correct answer: B. A missing or incorrect route entry on the network router.
If a server cannot reach resources on a different subnet despite correct local IP configuration (including gateway), and other devices on the same subnet can, it strongly suggests that the router responsible for forwarding traffic between the server's subnet and the destination subnet is missing a route or has an incorrect one.
Why the other options are wrong
- A. Incorrect DNS would cause name resolution failures, but not prevent direct IP connectivity to other subnets.
- C. Outdated drivers might cause general connectivity issues but would likely affect local subnet communication too, and wouldn't explain why only remote subnet access is failing.
- D. A broadcast storm would severely impact all devices on the local subnet, not just one server trying to reach a remote subnet.
Network Routing
The process of selecting a path across one or more networks to send data packets from a source to a destination.
- Routers use routing tables to determine paths.
- Essential for communication between different IP subnets.
- Incorrect or missing routes cause connectivity failures to remote networks.
Memory trick: When the path is blocked, check the map (routing table).