On Wed, May 22, 2002 at 02:31:57AM -0400, Derek Glidden wrote:
> On Tue, 2002-05-21 at 23:00, Smitty wrote:
> > Anyone know which keyboard characters one cannot use in a domain name?
> > Smitty
>
> RFC952 defines a hostname as:
>
> <name> ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]
>
> A "let" is a letter A-Z, digit is 0-9.
>
> RFC1123 relaxes it a bit: "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."
>
> So a FQDN must begin with only a letter or digit, use only letters,
> digits and hyphens in the name and conclude with only a letter or digit.
>
> Of course, you could create something that was otherwise, but it would
> likely break a lot of software trying to interact with it.
Yeah, it does:
in glibc (on linux) underscore in hostname is permitted.
on freebsd's (and as i understand it openbsd's) libc underscore in
hostname will cause DNS failures trying to communicate with _'d system.
To add to the confusion, RFC 1033 adds underscore to its list of
recommended characters. IMHO, underscore should not be permitted.
I went through this with a freebsd mail server trying to talk to a MS
(I think it was Win 2K pro) system. That was fun.
This archive was generated by hypermail 2.1.3 : Fri Aug 01 2014 - 19:09:29 EDT