reverse dns flow

Question

I am trying to understand the reverse dns implementation of bind. in my lab setup, i have a pxe server witn dns configured. it has 21.168.192.in-arpa.arpa reverse lookup zone file. i am using foreman to deploy remote machine. ip of my foreman server is 192.168.21.1/20.If i create any host in foreman, it creates reverse lookup entry in db file. if i try to assign ip to my client other than 21 in third octat ex- 192.168.22.101, foreman shows error with reverse dns. My understanding on this is that foreman is not able to find the db file 22.168.192.in-arpa.arpa and showing error. Is my configuration is wrong. should i create db file with network id or do i have to create separate file for each range.

Answer 1

Bind is the service responsible for reverse lookup, so that's where you have to go looking first.

You mention 192.168.21.0/20, but that actually covers 192.168.16.0-192.168.31.255 and since you say you have a 21.168.192.in-arpa.arpa it sounds like bind is misconfigured.

You will need to configure bind to include:

    zone "16/20.168.192.in-arpa.arpa" {
        type master;
        file "/path/to/a/new/16.168.192.in-arpa.arpa-db-file";
        allow-update {  key copy-this-from-the-other-reverse-zone; };
    }

the new db file should be something like:

    $TTL 2d ; 172800
    $ORIGIN 64/27.23.168.192.IN-ADDR.ARPA.
    @            IN  SOA   ns1.example.com. hostmaster.example.com. (
                          2003080800 ; serial number
                          3h         ; refresh
                          15m        ; update retry
                          3w         ; expiry
                          3h      ; nx = nxdomain ttl
                          )
          IN  NS      ns1.example.com.
          IN  NS      ns2.example.com.

For more information on bind and reverse lookup, see this link where i learned everything i know about bind