CompTIA Network+ (N10-009)Network TroubleshootingEasy
A network technician is troubleshooting a client workstation that can access local network resources but cannot reach any external websites or services. The technician pings the local gateway, which responds successfully. Next, the technician attempts to ping 8.8.8.8 (Google's public DNS server) and receives 'Request timed out.' messages. Which of the following is the MOST likely cause of this issue?
- AA firewall blocking outbound traffic on the network.
- BThe workstation's network interface card (NIC) is faulty.
- CIncorrect subnet mask configuration on the workstation.
- DThe local DHCP server is offline.
Show answer & explanationAnswer & explanation
Correct answer: A. A firewall blocking outbound traffic on the network.
The workstation can reach the local gateway, indicating local network connectivity is fine. The inability to ping an external IP address (8.8.8.8) but successful ping of the gateway strongly suggests that outbound traffic is being blocked beyond the local subnet, commonly by a firewall.
Why the other options are wrong
- B. A faulty NIC would typically prevent any network communication, including reaching the local gateway.
- C. An incorrect subnet mask would likely prevent access to the local gateway as well.
- D. If the DHCP server were offline, the workstation might not get an IP address, or if it had one, it would still likely be able to reach the gateway unless its lease expired and it couldn't renew.
Outbound Connectivity Issue
A problem where a device can communicate within its local network but cannot access resources outside of it.
- Often points to a gateway or firewall issue.
- Local pings succeed, external pings fail.
- DNS issues can also manifest similarly, but pinging an IP bypasses DNS.
Memory trick: Local is fine, but the 'door' to the outside is shut.