DNS : Troubleshooting - Part 1

image 1. TCP/IP Configuration Points to Public DNS Servers
A perfect TCP/IP configuration gives better communication performance of a Network.Check the TCP/IP Configuration twice or thrice to make sure everything configured perfectly. Try pinging the other servers in network using the names (not using IP's). Try NSLOOKUP, check the name resolution working correctly or not. If NSLOOKUP, gives any errors try checking the A records and PTR records for that server. Make sure the DNS server working correctly and the correct DNS server configured on the server you are working on.

2. Improper DNS Suffix Handling
If your computer is multi homed (multiple networks), make sure the DNS suffix is configured correctly for the correct interface. I mean, for every computer only one interface is configured with the suffix because every network only has one DNS server and this interface is configured to communicate with that DNS server. So make sure the interface which is communicating to DNS server must be configured with correct suffixes in order. These suffixes are used when you try to access a server on the network with its NetBIOS name, not with entire domain name. Because of this configuration you can able to access the server with NetBIOS name itself. No need to give entire DNS name like... ex.. server1.subdomain.domain.com. But simply you can access the

3. Improperly Configured Forwarding
DNS forwarders configuration is must for each and every DNS server as forwarders handle all the requests which are not handled by that DNS server. The requests which are not related to internal network also handled by forwarders only. so make sure correct forwarder is configured for the DNS server in your environment. Basically these are provided by your Internet service provider.

4. Improper DNS Configuration
In windows 2000/2003/2008 the DNS configuration is handled automatically by DCPROMO itself. When you try to install AD on a standalone server, as a part of the process DNS server application will be installed and configured automatically. Some times we may need to configure the DNS server manually. In that case we may forget to configure some service locator records(SRV) or other records which are required to run the DNS perfectly. We can fix these type of problems using "netdiag /fix" command.

5. Failure to Verify Dynamic Update of Resource Records
SOA record is very important in multi DNS server environments. Primary DNS server sends DNS updates automatically to Secondary DNS server depending on the SOA record number. When ever any update happens on the DNS server, the number of the SOA record will be incremented. This number should be same on both DNS servers, so that we can confirm that the both servers are in sync. Sometimes due to communication problems between Primary and Secondary these updates will not sync. Make sure both servers are pinging perfectly.


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