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Difficulty: MediumTroubleshooting DNS and Name Resolution Services

A network administrator is troubleshooting a client workstation that receives a name resolution error when attempting to reach an internal portal at `hrportal.contoso.com`. In what sequence should the administrator execute the following steps to systematically isolate the issue according to standard operating system name resolution precedence?

  1. 1Inspect the local HOSTS file for static entry overrides pointing to an outdated IP address.
  2. 2Flush the client's local DNS resolver cache using `ipconfig /flushdns` to clear stale records.
  3. 3Execute `nslookup hrportal.contoso.com` against the primary DNS server to test server-side record resolution.
  4. 4Perform a `ping` command against the resolved IP address to verify Layer 3 network reachability.

Answer

The correct order follows operating system resolution precedence: first inspect the local static HOSTS file, second flush the OS DNS resolver cache, third perform a direct `nslookup` against the DNS server, and fourth verify Layer 3 IP reachability using `ping`.
Troubleshooting follows OS resolution precedence: checking local HOSTS entries first, clearing the local resolver cache second, querying the DNS server directly via `nslookup` third, and testing IP connectivity via `ping` fourth once an IP is obtained.

Step-by-Step Solution

1
Examine the local HOSTS file.
Determines whether a local static text mapping is overriding network DNS resolution.
The OS evaluates the local HOSTS file prior to checking local DNS cache or issuing network queries.
2
Flush the client DNS cache using `ipconfig /flushdns`.
Purges cached negative responses or outdated A/AAAA records.
If no static HOSTS entry exists, the OS checks the local cache next.
3
Perform a direct DNS lookup using `nslookup hrportal.contoso.com`.
Verifies if the configured local DNS server has a valid, reachable record.
Bypasses local client caching mechanisms to isolate DNS server availability and record accuracy.
4
Test IP connectivity using `ping` to the resolved IP address.
Confirms whether network routing, firewalls, and server ports allow communication.
IP-level testing is only meaningful once name resolution yields an IP address.

Key Concept

OS Name Resolution Order and Systematic DNS Troubleshooting Sequence
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Topics

Troubleshooting DNS and Name Resolution Services

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