How do you test connectivity to a next-hop address in a router?

• A. Use traceroute to the next-hop address
• B. Use telnet to the next-hop address
• C. Use ssh to the next-hop address
• D. Use ping to the next-hop address

Answer: (D)

Testing connectivity to the next-hop address is about confirming basic reachability at the IP level. Ping does this most directly by sending an ICMP echo request to the next-hop IP and waiting for a reply. If you get a reply, the next-hop is reachable and the path to it is up at Layer 3. If you don’t receive a reply, there could be a link problem, the next-hop could be down, or ICMP might be blocked somewhere along the path, which still tells you there’s an issue to investigate.

Traceroute can diagnose the path and show where a problem occurs along the route, but it isn’t a simple confirmation of reachability to the next-hop itself and relies on intermediate devices responding to TTL-expired or ICMP messages, which some networks block. Telnet and SSH test whether a specific service on the next-hop is reachable, but they require that service to be running and accessible, and they don’t reliably indicate basic IP connectivity.