Multiple PTR records

[Chris Buxton]

On Jan 15, 2009, at 6:33 AM, Halassy Zoltán wrote:
> My configuration:
>
> Have a router, two computers behind it. comp1 has webserver (no  
> mailserver), comp2 has mailserver (no webserver), have one IPv4  
> address, and few IPv6 addresses. The IPv4 address configured on the  
> router, DNAT-ing the TCPv4 ports to one of the computers (80 ->  
> comp1, 25 -> comp2, etc). IPv6 is natively routed.
>
> I don't want to break forward <-> reverse mapping.
>
> So the config would be something like this:
>
> example.com. MX 10 mail.example.com.
> www.example.com. A 1.2.3.4
> mail.example.com. A 1.2.3.4
> www.example.com. AAAA 2001::1234:1
> mail.example.com. AAAA 2001::1234:2
> 1.0.0.0.4.3.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.2 
> .ip6.arpa. PTR www.example.com.
> 2.0.0.0.4.3.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.2 
> .ip6.arpa. PTR mail.example.com.
> 4.3.2.1.in-addr.arpa. PTR www.example.com.
> 4.3.2.1.in-addr.arpa. PTR mail.example.com.
>
> Would this one break anything? Or anyone else have a better tip how  
> could i handle this situation? Multiple PTRs in this case is really  
> an issue?

Yes, it is an issue. Remove this record:

4.3.2.1.in-addr.arpa. PTR www.example.com.

Your web server doesn't need a PTR record.

> The main thing i don't want to break forward <-> reverse symmetry  
> cause there are some sanity checks about this (like in spamfiltering).

Right, your mail server ought to have a PTR record. Your web server,  
however, does not need it.

Chris Buxton
Professional Services
Men & Mice