PTR-Records with Host-Header

[Kevin Darcy]

nobull at mail.com wrote:

> Roberto Rotondo <rotondo at bluewin.ch> writes:
>
> > Hello
> >
> > I want to deploy 3 Web-Sites with host headers. This are the 3 A-records
> > in my Zone:
> >
> > server1 212.28.166.33
> > server2 212.28.166.33
> > server3 212.28.166.33
> >
> > Should I create 3 PTR-entrys in the revers-lookup-zone???
>
> You can if you want.  It probably makes no difference.  Some resolvers
> do not properly handle multiple PTR RRs.

Most if not all resolver routines only look at the first record in an RRset
for a reverse lookup. Because of this, BIND does not apply RRset-ordering
(default "cyclic") to PTR RRsets; otherwise, multi-record PTR RRsets could
cause non-deterministic, seemingly-random behavior, which can cause
hard-to-troubleshoot application problems. As it is, the behavior is
deterministic, but it's a waste to have multi-record PTR's, since
most-if-not-all resolvers won't see beyond the first one.

> I would do:
>
> server1 A 212.28.166.33
> server2 CNAME server1
> server3 CNAME server1
>
> 33.166.28.212.in-addr.arpa PTR server1.example.com.

So would I, if I could, but if "server2" and/or "server3" are at a zone apex,
e.g. server2=example.com, then CNAMEs are of course not an option...


- Kevin