A user on a Windows workstation reports that navigating to `portal.corp.local` in a web browser leads to a 'Connection Refused' error. A network technician runs `nslookup portal.corp.local` and receives a successful authoritative response pointing to `192.168.10.45`. However, running `ipconfig /displaydns` on the client workstation reveals the following output:
text
Record Name . . . . . : portal.corp.local
Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 127.0.0.1
Which of the following is the root cause of the name resolution failure?
- A static entry in the client workstation's local HOSTS file is mapping the domain to the loopback address.Cevap
- BThe DNS server is missing an authoritative AAAA record for portal.corp.local.
- CAn upstream firewall is blocking TCP port 53 traffic required for standard DNS queries.
- DThe nslookup utility bypassed the local resolver cache and returned an unverified cached response from an external recursive server.
Cevap
A static entry in the client workstation's local HOSTS file is mapping the domain to the loopback address.
Operating systems check local resolution mechanisms (such as the HOSTS file) prior to sending DNS requests across the network. Entries in the HOSTS file are cached locally with a TTL of 86400 seconds. Because `nslookup` bypasses local system resolution to directly query DNS servers, it received the valid IP address (`192.168.10.45`), whereas application traffic from the web browser utilized the local cache entry pointing to `127.0.0.1`.
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Anahtar Kavram
Local HOSTS file precedence over DNS server queries and DNS cache behavior