How to isolate DNS vs. network issues?

How to isolate DNS vs. network issues?

• A. Resolve with dig; if IP works but name doesn't, it's a DNS issue.
• B. Reboot the DNS server.
• C. Inspect only the firewall logs.
• D. Ping to a host name repeatedly.

Answer: (A)

Isolating DNS versus network issues comes from separating name resolution from direct IP connectivity. Use a DNS query tool to resolve the host name to an IP. If you obtain an IP and can reach that IP, the network path is functioning and the problem is with DNS resolution. If the DNS query fails or returns no address, while you cannot reach the host by name, the issue lies with DNS. This approach cleanly distinguishes whether the problem is in locating the host (DNS) or in reaching it once you have an address (network). The other options don’t provide a reliable diagnostic path: rebooting the DNS server doesn’t diagnose where the failure occurs; inspecting only firewall logs misses DNS traffic behavior; and pinging by name relies on DNS and can be inconclusive if DNS is blocked or cached.

Isolating DNS versus network issues comes from separating name resolution from direct IP connectivity. Use a DNS query tool to resolve the host name to an IP. If you obtain an IP and can reach that IP, the network path is functioning and the problem is with DNS resolution. If the DNS query fails or returns no address, while you cannot reach the host by name, the issue lies with DNS. This approach cleanly distinguishes whether the problem is in locating the host (DNS) or in reaching it once you have an address (network). The other options don’t provide a reliable diagnostic path: rebooting the DNS server doesn’t diagnose where the failure occurs; inspecting only firewall logs misses DNS traffic behavior; and pinging by name relies on DNS and can be inconclusive if DNS is blocked or cached.