reverse dns for IPV6 ranges

Spain, Dr. Jeffry A. spainj at
Mon Mar 5 21:15:53 UTC 2012

> Can anyone help me with  its experience on reverse dns for IPV6?
> Presently, when we reverse an IPV4 subnet for clients, we configure all the reverse for the whole subnet.
> It is a lot of PTR's but perfectly manageable.
> With IPV6,  the number of IP's that we will receive is amazing....
> seems impossible for every single IPV6 inthe range to configure a PTR.
> So...what to do?
> What is the common practice?
> What is possible with BIND?

For our IPv6 address space 2001:4870:20ca::/48, I created a reverse lookup zone and arranged for delegation from our ISP.  I included PTR records only for those hosts accessible from the outside. Internal DNS is Windows Active Directory integrated. Here's a sample from the zone file, which contains about 25 PTR records in all:

$TTL 3600       ; 1 hour IN SOA (
                                2012030101 ; serial
                                86400      ; refresh (1 day)
                                3600       ; retry (1 hour)
                                1209600    ; expire (2 weeks)
                                3600       ; minimum (1 hour)
a.5.6.9.f.9.e. PTR
2.9.1.f.1.d.2.1.b.f.7.5.7.f.8.0 PTR

I would also be interested in hearing about the practices of others. Jeff.

Jeffry A. Spain
Network Administrator
Cincinnati Country Day School

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