When attempting to join a client machine to a domain,  you may receive the following error message, The format of the specified network name is invalid.  A leading cause for this error message is the DNS configuration on the client machine.

The first step you should perform is to ensure that the  DNS configuration on your client is pointing to the correct DNS server.  In many cases the DNS role is also hosted one of the domain controllers in  your domain.

To do this perform the following steps (the directions below reflect a Windows 7 client machine):

1.  Click Start, click Control Panel, click Network and Sharing, click Change adapter settings, and then double click your network adapter.

2.  Click Properties and then click Internet Protocol Version 6 (TCP/IPv6) or Internet Protocol Version 4 (TCP/IPv4) (whichever applies to your environment).

3.  Click Use the following DNS server addresses and under Preferred DNS server, enter the IP address of your DNS server.

You can also configure your domain environment to obtain a DNS server address automatically.  For more information on how to do this see,

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