Troubleshooting DNS

Most often, Domain Name System (DNS) configuration problems are exposed when one or more DNS client computers cannot resolve host names.

To troubleshoot DNS problems, you must determine the scope of the problem. To do this, you use the ping command on multiple clients to resolve the names of hosts on the intranet and the Internet, and to test overall network connectivity. Run the following commands on several DNS client computers and with several target computers, and then note the results:

·      ping DNS_server_ip_address

·      ping internal_host_ip_address, where internal_host_ip_address is the IP address of a computer that exists in the client's domain

·      ping internal_host_name, where internal_host_name is the fully qualified domain name (FQDN) of the computer

·      ping Internet_host_name, where Internet_host_name is the name of a computer that exists on the Internet.

Note

It is not important whether an Internet computer responds to the ping command. What is important is that DNS can resolve the name that you specify to an IP address.

The results of these tests suggest the nature of the problem. The following table shows possible results, causes, and solutions.

ping command result	Possible cause	Possible solution
Multiple clients cannot resolve any intranet or Internet names	This result suggests that the clients cannot access the assigned DNS server. This might be the result of general network problems, particularly if the ping command using IP addresses fails. Otherwise, if you have configured the clients to obtain DNS server addresses automatically, you might not have configured the Dynamic Host Configuration Protocol (DHCP) servers on the network properly.	Review the configuration of the DHCP servers on the network.
Multiple clients cannot resolve intranet names, but they can resolve Internet names	This result suggests that host (A) resource records, or records such as service locator (SRV) resource records, do not exist in the DNS zone database. Also see "One client only cannot resolve intranet names, only Internet names."	Ensure that the appropriate resource records exist and that you have configured the DNS server properly to receive automatic updates. If the target host names are located in a particular child zone, ensure that you have configured delegation of that zone properly. To test registration of records for a domain controller, use the dcdiag /test:dns /v /s:domain_controller command.
One client only cannot resolve any intranet or Internet names	If the ping command using IP addresses fails, this result indicates that the client computer cannot connect to the network. If the ping command using IP addresses succeeds, but the ping command cannot resolve DNS domain names, the TCP/IP settings of the client may be incorrect.	Ensure that the client computer is physically connected to the network and that the network adapter for the computer functions properly, or correct the TCP/IP settings, as necessary. To correct the settings, see Configuring Client Settings.
One client only cannot resolve intranet names, only Internet names	If you previously configured the client computer to connect directly to the Internet, its TCP/IP properties might be configured to use an external DNS server, such as a DNS server from an Internet service provider (ISP). In most cases, the client should not use a DNS server from an ISP as either the preferred or alternate DNS server because the DNS server at the ISP is not able to resolve internal names. Using a DNS server from an ISP in the TCP/IP configuration of a client can also cause problems with conflicting internal and external namespaces.	To correct the settings, see Configuring Client Settings.

If you have ruled out all of these potential problems for a particular client and still cannot resolve DNS names, use the procedures in Configuring Client Settings to verify the DNS client settings. Then, at a command prompt, type ipconfig /all to view the current TCP/IP configuration.

If the client does not have a valid TCP/IP configuration, you can perform one of the following tasks:

·      For dynamically configured clients, use the ipconfig /renew command to manually force the client to renew its IP address configuration with the DHCP server.

·      For statically configured clients, modify the client TCP/IP properties to use valid configuration settings or to complete its DNS configuration for the network.