[dns-operations] about the underline in hostname

Mark Andrews marka at isc.org
Fri May 30 02:18:59 UTC 2014

In message <5387E556.5070902 at arcor.de>, hua peng writes:
> IIRC BIND doesn't permit an A record whose label has a underscore 
> included, for example, this one:
> aa_bb.google.com.         300     IN      A
> what RFC item is it influenced by?
> Thanks.

RFC 952, RFC 1123 and RFC 1034.  Now if aa_bb.google.com is not a
host you can turn the check off but 99.9999% of the time the owner
name of a A record is being used as a hostname.

> > BIND does allow domain names with underscores in them. In fact SRV records 
> use underscores so that names with those _service._proto labels can't be conf
> used with hostnames.
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Mark Andrews, ISC
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