Why can servers ping each other but not reach the internet?
An engineer recently installed a new distribution switch and connected two servers provisioned with the following IPs: 192.168.17.20 and 192.168.17.30. The servers cannot connect to the internet, but they can reach themselves. The engineer observes that the distribution switch has the following setup: interface VLAN 100 IP address 192.168.17.5 255.255.255.0 The engineer is able to reach the core router 192.168.17.1 from the distribution switch. Which of the following is the most likely cause of this issue?
Community Votes
100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
This question tests the Layer 3 requirement that hosts need a default gateway to forward traffic outside their own subnet; the common trap is overlooking that local connectivity succeeds without a gateway.
When servers on the same VLAN can communicate internally but cannot reach the internet, the most likely cause is a missing or incorrect default gateway configuration. Community consensus strongly supports option C, as the distribution switch can already reach the core router.
Choosing 'The subnet mask is incorrect' or 'A routing loop has occurred' because both can cause partial reachability, but here the servers are on the same /24 subnet and the switch can reach the router, making a missing default gateway the only logical cause.
Community Discussion (3 comments)
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Expert Analysis
Why the Answer Is Correct
Option C is correct because the servers have valid IP addresses on the same subnet and can communicate locally, but they have no path to the internet. A host must have a default gateway (usually the router or Layer 3 switch interface) configured to send packets to destinations outside its own network. The distribution switch can reach the core router, so routing infrastructure is functioning; the failure is at the server's gateway configuration.Why the Other Options Are Wrong
A routing loop would cause packets to be forwarded cyclically and would typically show symptoms even from the switch, while the switch can reach the router normally. An incorrect subnet mask would likely cause problems communicating even within the /24 subnet, yet the servers reach each other. A Layer 1 issue with the router-to-ISP connection would not prevent the servers from reaching the distribution switch or each other, and the question indicates the switch can reach the core router.Community Comment Notes
All provided comments simply select option C with similar reasoning — that internal connectivity works while external connectivity fails, pointing to gateway misconfiguration. No dissenting answers or alternative explanations appear in the comments, reinforcing that this is a standard default-gateway troubleshooting scenario.Official Reference
Exam Strategy
When troubleshooting reachability, use the command-line tools ping and tracert/traceroute to map where the path fails. If local pings succeed but remote pings fail, the first configuration to verify is the default gateway on the host and the routing table on the gateway device.