Article ID: 122900 - Last Review: January 19, 2007 - Revision: 4.3

Can't Use Periods in DNS Host Names

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This article was previously published under Q122900

SUMMARY

Both the Help file and the manual for the TCP/IP Domain Name Server (DNS) configuration are incorrect in describing the type of characters that can be used in the host name. The documentation says that both the hyphen and period can be used. However, attempting to use a period in the host name will result in an error message indicating the parameter is incorrect.

The TCP/IP manual says:

In the DNS Configuration dialog box, you can, optionally, type a name in the Host Name box (usually your computer name):

The name can be any combination of A-Z letters, 0-9 numerals, and the hyphen (-) plus the period (.) character used as a separator. By default, this value is the Windows NT computer name, but the network administrator can assign another host name without affecting the computer name.

The Help file says:

Host Name

Optionally, type a name in the Host Name box (usually your computer name). The name can be any combination of A-Z letters and 0-9 digits, plus the hyphen (-) and period (.) characters.

Using a period in the host name would be interpreted as a separator, and result in an error message.

RFC 952 says:

Periods are only allowed when they serve to delimit components of "domain style names".

The Windows 95 Resource Kit states:

To set the host name for DNS

Type a name in the Host Name box.

The name can be any combination of the letters A through Z, the numerals 0 through 9, and the hyphen (-), plus the period (.) character used as a separator. By default, this value is the Microsoft networking computer name, but the network administrator can assign another host name without affecting the computer name.

Note: Some characters that can be used in computer names, especially the underscore, cannot be used in host names.

The Windows 98 Resource Kit states:

Microsoft TCP/IP Protocol

Using DNS for Name Resolution

Configuring DNS

To set the host name for DNS

Type a name in the Host box. The name can be any combination of the letters A through Z, the numerals 0 through 9, and the hyphen (-), plus the period (.) character used as a separator. By default, this value is the Microsoft networking computer name, but the network administrator can assign another host name without affecting the computer name.

MORE INFORMATION

Under Windows NT 3.5, the host name is set to the computer name (or NetBIOS name) by default. You can change the name used from the Network section of Control Panel. Select TCP/IP Protocol, choose Configure, and then choose DNS to see the host name. You can specify both the host and domain names.

NOTE: The domain name listed here should not be confused with the term "domain name" as it is used in a Windows NT domain. This is the domain name set by the TCP/IP DNS.

Reference(s):

More information on DNS can be found in the DNS RFC 1034.