$ORIGIN .
$TTL 86400      ; 1 day
20.27.172.in-addr.arpa     IN SOA  master-dns.lavalab. postmaster.lavalab. (
                                2019121602 ; serial
                                28800      ; refresh (8 hours)
                                7200       ; retry (2 hours)
                                2419200    ; expire (4 weeks)
                                86400      ; minimum (1 day)
                                )
                        NS      ns.lnglab.
$ORIGIN 20.27.172.in-addr.arpa.
111                     PTR     router.lnglab.