single-character host names

Mike Bernhardt bernhardt at
Thu Feb 26 18:03:07 UTC 2009

Another wrinkle: RFC 1035 states "The labels must follow the rules for
ARPANET host names.  They must start with a letter, end with a letter or
digit, and have as interior characters only letters, digits, and hyphen.
There are also some restrictions on the length.  Labels must be 63
characters or less."

RFC 1123 states " The syntax of a legal Internet host name was specified in
RFC-952 [DNS:4].  One aspect of host name syntax is hereby changed: the
restriction on the first character is relaxed to allow either a letter or a
digit.  Host software MUST support this more liberal syntax.

Host software MUST handle host names of up to 63 characters and SHOULD
handle host names of up to 255 characters."

It does not mention RFC 1035 label requirements also being updated, though
obviously using digits as first characters is now quite common. It also
implies that RFC952 is indeed the reference document to work from. Mighty


-----Original Message-----
From: Matthew Pounsett [mailto:matt at] 
Sent: Wednesday, February 25, 2009 2:34 PM
To: Evan Hunt
Cc: Mike Bernhardt; bind-users at
Subject: Re: single-character host names

>The OP should be looking to RFC1035 section 2.3.1 for the  
>specification for modern host names.

More information about the bind-users mailing list