SK0-004 · Question #232
A user is unable to connect to the companys intranet server by FQDN, but can connect by IP address. Other users are not having a problem. An administrator verifies that the user can successfully…
The correct answer is D. Examine the hosts file. When nslookup resolves an FQDN correctly but connection by FQDN still fails after flushing the DNS cache, the local hosts file likely contains a conflicting or incorrect entry that overrides DNS.
Question
A user is unable to connect to the companys intranet server by FQDN, but can connect by IP address. Other users are not having a problem. An administrator verifies that the user can successfully ping the server by IP address and can properly resolve the FQDN using nslookup. The problem is persisting after running ipconfig /flushdns. Which of the following should the administrator do NEXT?
Options
- AExamine the lmhost file.
- BFlush the cache on the DNS server.
- CFlush the cache on the WINS server.
- DExamine the hosts file.
How the community answered
(45 responses)- A9% (4)
- B4% (2)
- C20% (9)
- D67% (30)
Why each option
When nslookup resolves an FQDN correctly but connection by FQDN still fails after flushing the DNS cache, the local hosts file likely contains a conflicting or incorrect entry that overrides DNS.
The lmhosts file is used for NetBIOS name resolution, not FQDN-based DNS resolution; connecting to an intranet server by fully qualified domain name does not use lmhosts.
Flushing the DNS server cache would affect all clients resolving that name, but since only this one user is experiencing the problem, the DNS server cache is not the source of the issue.
WINS resolves NetBIOS names rather than FQDNs; the problem involves FQDN-based resolution, so the WINS server cache is not relevant here.
The hosts file is parsed before DNS resolution occurs; if a stale or incorrect IP mapping exists for the FQDN in that file, the OS uses it instead of querying DNS - explaining why nslookup (which queries DNS directly) succeeds while the actual connection fails, and why flushing the DNS client cache had no effect since the hosts file is not part of that cache.
Concept tested: Local hosts file overriding DNS FQDN resolution
Source: https://learn.microsoft.com/en-us/windows-server/networking/dns/troubleshoot/troubleshoot-dns-client
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