check-nsservers-know

#!/usr/bin/perl -w
use strict;
use warnings;
use Net::DNS;

# takes a single domain, retrieves the ns records for it and then
# queries each server to ensure it can answer for that domain

my $domain = shift;

my $res   = Net::DNS::Resolver->new;
my $query = $res->query( $domain, "NS");

if ($query) {
  foreach my $rr (grep { $_->type eq 'NS' } $query->answer) {
    $res->nameservers( $rr->nsdname);

    my $lookup = $res->query( $domain, "A");
    if ($lookup) {
      foreach my $record (grep { $_->type eq 'A' } $lookup->answer) {
        print $domain, " ", $rr->nsdname, " ", $record->address, "\n";
      }
    } else {
      warn "A record query for [$domain] against [", $rr->nsdname, "] failed: ", $res->errorstring, "\n";
    }
  }
} else {
  warn "NS record query for [$domain] failed : ", $res->errorstring, "\n";
}