Performance Issues - PTR Records

Mark Andrews marka at
Sun Nov 6 19:10:21 CST 2011

In message <FA83E0C6-DAFC-4C8C-AF46-826EDF4727F8 at>, Tom Lanyon wri
> On 05/11/2011, at 1:14 PM, Paul Ebersman wrote:
> > tim> If PTR exists in zone file, serve it.  Else, synthesize generic
> > tim> reverse.  Jobsagoodun.
> >=20
> > If all we're doing is lying with some generic answer that we hack our
> > server to produce, why are we bothering?
> Because some applications rely on it working (for some definition of =
> "working").
> > My contention is that (at least for end hosts), PTR records are mostly
> > pointless and just overhead for DNS servers.
> If you haven't set up PTR records for your end hosts, realistically =
> you're going to be serving NXDOMAINs for them anyway, so there's not =
> really any overhead introduced by supplying something generic instead...
> Tom

Except you also have to supply the A/AAAA records as well.

MacOS and Windows can both populate the reverse zone for you as can
dhcp servers.

The practice of filling out the reverse zone with fake PTR record
started before there was wide spread support for UPDATE/DNS.  There
isn't any need for this to be done anymore.  Machines are capable
of adding records for themselves.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

More information about the NANOG mailing list