taca@back-street.net said:
>  AFAIR, hostname; A or AAAA record dosen't allow '_' in leaf label. 

Generally yes -- RFC1123 allows only alphanumeric and hyphen chars.
Tolerating the "_" would be in the spirit of "be liberal in what
you accept".
In the world out there, there are DNS entries like www.aka.fi's,
and there are operating systems like Linux and Solaris which
don't complain about it. (Google told me that also Windows
allows it, but I did check only the former two myself.)

Newer versions of the resolver lib which comes with BIND support
an option "no-check-names" to switch off the strict check
for characters in hostnames. The parsing code is already there,
just NetBSD's nss glue code was not updated. This is trivial to
pull in -- I'll post patches to tech-userlevel.
Allowing each administrator to decide for himself looks like
a reasonable compromise to me.

best regards
Matthias