Troubleshooting DNS

NSLOOKUP is an important utility that performs query testing and troubleshooting of DNS servers at the command prompt window. NSLOOKUP can be accessed by going to the command prompt window and typing in NSLOOKUP and pressing Enter.

Use the buttons below to navigate through the lesson

As shown, the NSLOOKUP tool is now active. To do a forward or reverse lookup, type the name in the command prompt window. A list of command lines can be found by typing in help or ? From the NSLOOKUP command window.

When a query is made to a DNS server, the server can either return an authoritative answer or a non-authoritative answer. If it returns an authoritative answer then the record exists in its own zone file. If it returns a non-authoritative answer then the record exists in the zone file of another DNS server.

There are many ways that DNS can fail to work. There is no one sure way to solve every problem which might occur. The following list is a reasonable starting point for troubleshooting.

  1. Test to see if the client is on the network by using the “ping” utility.
  2. Use “ipconfig” to view the clients DNS settings.
  3. Use NSLOOKUP to perform DNS queries and check the contents of the zone files.
  4. Use the Event Viewer to see any DNS client or server error messages.
  5. From the server Properties choose the Logging tab to log and monitor certain events.
  6. From the server Properties choose the Monitoring tab to perform simple test queries.
  7. From the DNS console select Action and choose Set Aging/Scavenging to clear the DNS database of stale resource records.

While Ping, Ipconfig and Nslookup can all be run in a command window with the ? Switch to reveal the full range of available configurations, there are two switches in particular which are used more often than others in troubleshooting DNS:

Ipconfig /flushdns – empties the local resolver cache. (This cache is the file of all the names and addresses resolved for the client so far.)

Ipconfig /registerdns – forces a dynamic update of the client’s registration in the local DNS server..