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Zorluk: ZorTroubleshooting DNS and Name Resolution Services

A network technician is investigating a client workstation that fails to resolve the internal hostname `app.finance.local`. Place the following diagnostic steps in the correct order, starting from initial client configuration verification through transport layer troubleshooting.

  1. 1Run `ipconfig /all` on the workstation to verify that a valid local IP address and correct primary DNS server IP address are configured.
  2. 2Inspect the local `HOSTS` file for incorrect static mappings and execute `ipconfig /flushdns` to clear local resolver cache entries.
  3. 3Execute `nslookup app.finance.local` targeting the assigned DNS server IP directly to test domain record query response.
  4. 4Perform a port check using `Test-NetConnection 192.168.1.10 -Port 53` to verify that firewall rules or ACLs are not blocking DNS traffic.

Cevap

The proper troubleshooting sequence moves from local client IP configuration verification, to clearing local host resolution mechanisms (HOSTS file and DNS resolver cache), to testing direct DNS server resolution via `nslookup`, and finally checking transport connectivity on port 53.
A methodical name resolution troubleshooting workflow starts by validating client IP/DNS configuration, clearing local client-side caches and static lookup overrides, querying the designated DNS server directly to test record availability, and lastly verifying port 53 reachability if timeouts occur.

Adım Adım Çözüm

1
Verify client TCP/IP configuration
Confirms the workstation possesses a valid IP, subnet mask, default gateway, and correct DNS server IP.
Troubleshooting should start at Layer 3 client settings to ensure the endpoint knows which DNS server to query.
2
Check and clear local name resolution state
Eliminates bad static overrides in the local `HOSTS` file and flushes stale cache records.
Operating systems query local file maps and DNS resolver caches prior to sending network DNS requests.
3
Perform direct DNS resolution query
Determines whether the DNS server returns an IP address, an NXDOMAIN error, or a server failure response.
Direct diagnostic tools like `nslookup` bypass local caching to evaluate DNS server operational status and zone records.
4
Verify transport layer filtering and reachability
Identifies if firewall ACLs or intermediate network devices are dropping UDP or TCP port 53 traffic.
If DNS queries time out completely, network access controls or port-level filtering must be diagnosed.

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