This information HAS errors and is made available WITHOUT ANY WARRANTY OF ANY KIND and without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. It is not permissible to be read by anyone who has ever met a lawyer or attorney. Use is confined to Engineers with more than 370 course hours of engineering.

DNS and reverse delegation

Configuration of Bind for reverse DNS PTR records classless

Once your ISP has configured reverse delegation you can see it with dig.

# dig +trace -x123.2.3.4

Near the end you will see a CNAME statement something like this:

??????????????????? CNAME 4.24/

or this

??????????????????? CNAME


??????????????????? CNAME 4.0-

The format of these CNAMEs are not standard and it appears one needs to create a separate zone for each IP address - bind does not seem to understand any of these besides the class specific ones such as:


So in your named.conf.local file your zone statement looks like this

zone "4.24/" IN {
 type master;
 file "/etc/bind/db.";

In the zone file you need something like this:

$TTL 345600
@ IN SOA ns1.example.com. hostmaster.example.com. (
 2014032000  ; serial-date+2digit
 12000  ; refresh
 900  ; retry
 120000  ; expire
 3600)  ; minimum TTL
 NS ns1.example.com.
 NS ns2.example.com.
 PTR example.com.
 TXT "v=spf1  ip4: -all"
 SPF "v=spf1  ip4: -all"

Top Page wiki Index