BIND create reverse zone for /21 block

Question

LINUX, BIND9

I have a network which sits in /21 block and would like to make a reverse zone, I would like some guidance to know where to look to create the reverse zone file.

I could make seperate files for each of the 3rd octet block, example: 0.168.192.in-addr.arpa.zone + 1.168.192.in-addr.arpa.zone +.... 7.168.192.in-addr.arpa.zone. But how would I combine this into one file and put all the PTR records in the same place?

somebody · Answer 1 · 2019-06-21T19:26:00.760

Create a zone like you would for any other host/domain.

Lets call it 1.168.192.in-addr.arpa.zone:

$TTL    3600
$ORIGIN 1.168.192.in-addr.arpa.
@   IN SOA  primary.domain.name.    root.localhost. (
            2016010220  ; Serial
            3600        ; Refresh (1hr)
            300         ; Retry (15min)
            3600000     ; Expire (5 weeks 6 days 16 hours)
            3600  )     ; Minimum (1hr)

; authoritative servers
            IN  NS  primary.domain.name.
            IN  NS  secondary.server.name.
            IN  NS  slave.dome.domain.
            IN  NS  ...
            IN  NS  ...

; RRs
1.1.168.192.in-addr.arpa.   IN  PTR host.domain.name.
2.1.168.192.in-addr.arpa.   IN  PTR nameserver.some.domain.
3.1.168.192.in-addr.arpa.   IN  PTR another.host.name.

...

253.1.168.192.in-addr.arpa. IN  PTR mx.mail.exchange.
254.1.168.192.in-addr.arpa. IN  PTR web.server.domain.

Then list it as you would any other zone in your named.conf file. That's really all you need.

EDIT:

It occurs to me based on your respnse in the comments section that you might not be familiar with CIDR notation

Here's a CIDR calculator from the authority on Internet Numbers (ARIN).

As such. Here's another way to describe an entire block of (IP) 256 addresses:

192.168.1.0/24

The notation is the same as described above. But you're now able to "group" blocks of varying quantity in each delegation.

You can also describe "blocks" of IP addresses thusly:

0-256    IN NS master.some.domain

or

1.0-3.0.168.192.in-addr.arpa    IN  PTR  host.domain.name.

In your RR glue (as above).

See also The BIND Administration Guide for the proprietary $GENERATE macro for creating sequences of PTR records (assumes a "classfull" list).

Lastly, an RFC2317 example you might find helpful

$ORIGIN 2.0.192.in-addr.arpa.
@       IN      SOA     my-ns.my.domain. hostmaster.my.domain. (...)
;...
;  <<0-127>> /25
0/25            NS      ns.A.domain.
0/25            NS      some.other.name.server.
;
1               CNAME   1.0/25.2.0.192.in-addr.arpa.
2               CNAME   2.0/25.2.0.192.in-addr.arpa.
3               CNAME   3.0/25.2.0.192.in-addr.arpa.
;
;  <<128-191>> /26
128/26          NS      ns.B.domain.
128/26          NS      some.other.name.server.too.
;
129             CNAME   129.128/26.2.0.192.in-addr.arpa.
130             CNAME   130.128/26.2.0.192.in-addr.arpa.
131             CNAME   131.128/26.2.0.192.in-addr.arpa.
;
;  <<192-255>> /26
192/26          NS      ns.C.domain.
192/26          NS      some.other.third.name.server.
;
193             CNAME   193.192/26.2.0.192.in-addr.arpa.
194             CNAME   194.192/26.2.0.192.in-addr.arpa.
195             CNAME   195.192/26.2.0.192.in-addr.arpa.

$ORIGIN 0/25.2.0.192.in-addr.arpa.
@       IN      SOA     ns.A.domain. hostmaster.A.domain. (...)
@               NS      ns.A.domain.
@               NS      some.other.name.server.
;
1               PTR     host1.A.domain.
2               PTR     host2.A.domain.
3               PTR     host3.A.domain.

HTH

BIND create reverse zone for /21 block

1 Answers1