Question

Difficulty: EasyTroubleshooting DNS and Name Resolution Services

A user on a Windows client workstation reports being unable to connect to an internal web application at `intranet.corp.local` after the server was migrated to a new IP address (`192.168.1.50`). A technician executes `ipconfig /displaydns` on the client workstation and receives the following output:

text
Record Name . . . . . : intranet.corp.local
Record Type . . . . . : 1
Time To Live . . . . : 86400
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 192.168.1.250

Which TWO of the following actions or events will resolve this name resolution issue on the client workstation? (Select TWO.)

  1. Run the `ipconfig /flushdns` command on the client workstation.Answer
  2. Wait for the 86400-second Time To Live (TTL) period of the cached entry to expire.Answer
  3. C
    Run the `ipconfig /registerdns` command on the client workstation.
  4. D
    Reconfigure the client resolver to send DNS queries over TCP port 53 instead of UDP port 53.

Answer

The issue is resolved by running `ipconfig /flushdns` to immediately purge the stale cached record, or by allowing the entry's Time To Live (TTL) duration to naturally expire.
The client workstation is resolving the hostname to an outdated IP address because the entry is saved in the local OS DNS resolver cache. Executing the command to flush the DNS cache immediately purges all cached entries, forcing the workstation to perform a fresh DNS query against the server. Alternatively, allowing the Time To Live (TTL) timer of 86,400 seconds to naturally expire will cause the operating system to automatically remove the stale entry from memory.

Step-by-Step Solution

1
Analyze the `ipconfig /displaydns` output.
The workstation has cached an A record for `intranet.corp.local` pointing to the old IP address (`192.168.1.250`) with a TTL of 86,400 seconds (24 hours).
When a host has an entry stored in its local DNS resolver cache, it uses that cached mapping without querying the configured DNS server.
2
Identify methods to remove stale DNS resolver cache entries.
Manually clearing the cache via `ipconfig /flushdns` or waiting for the TTL timer to count down to 0 will remove the outdated entry.
Removing the stale entry forces the client operating system to send a fresh DNS query to the DNS server, returning the updated IP address (`192.168.1.50`).

Key Concept

Stale DNS Resolver Cache and TTL Management
Rate this question