reasonable length of FQDN

Gregory Hicks ghicks at
Wed Feb 1 19:01:49 UTC 2006

> To: comp-protocols-dns-bind at
> From: Christian Smith <csmith.lunchmeat at>
> Subject: Re: reasonable length of FQDN
> Date: Wed, 01 Feb 2006 12:19:10 GMT
> In article <drphne$cog$1 at>,
>  Roman Mashak <romez777 at> wrote:
> > Hello,
> > 
> > what may be the reasonable length of fully-quialilfied domain name
> > that can be set up in application? I'd wish this length would cover
> > possible user desires and at the same time wouldn't violate standard.
> 255 characters assuming one octet per character. 

Some OSes, however, further limit the HOST portion of the FQDN...
HP-UX, for example, limits the host name to a measly 8 chars.  And if
someone tells me that an HP-UX host name can be longer than 8 chars, I
can tell them that HP-UX only looks at the first 8 chars when trying to
do a match...

>    The DNS itself places only one restriction on the particular labels
>    that can be used to identify resource records.  That one restriction
>    relates to the length of the label and the full name.  The length of
>    any one label is limited to between 1 and 63 octets.  A full domain
>    name is limited to 255 octets (including the separators).


I am perfectly capable of learning from my mistakes.  I will surely
learn a great deal today.

"A democracy is a sheep and two wolves deciding on what to have for
lunch.  Freedom is a well armed sheep contesting the results of the
decision." - Benjamin Franklin

"The best we can hope for concerning the people at large is that they
be properly armed." --Alexander Hamilton

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