> > This suggestion has been superceded, or perhaps better elucidated, by > later RFC's, particularly RFC 2181, section 10.2. > > Nowadays many of us have reverse-DNS delegation in place since as an > end-user we have no control over the in-addr.arpa records for our > particular IP subnet. For instance, mail.cyways.com resolves to > 12.148.244.151, but a reverse query for that address yields: > > # host -t ptr 151.244.148.12.in-addr.arpa > 151.244.148.12.in-addr.arpa is an alias for > 151.128/27.244.148.12.in-addr.arpa. > 151.128/27.244.148.12.in-addr.arpa domain name pointer mail.cyways.com. > > That's because the 244.148.12.in-addr.arpa zone belongs to our provider > (AT&T), but they have delegated our /27 subnet's zone to us via this > aliasing process. RFC 2181 makes clear that aliasing is fine in the PTR > resolution process as long as the aliasing eventually points to a > canonical name like mail.cyways.com. > > This is a much better solution than requiring us to go to the provider to > update their PTR records every time we change the names of the hosts in > our subnet. RFC's like 1912 reflect a time when most people had control > over both forward and reverse name service for a class-A, B, or C IP > block. That came to an end when "classless," or "CIDR," addressing > became the norm. > > > Peter
Delegation of reverse DNS is not hard at any size block of IP addresses if the authoritative company will allow your name servers to be authoritative "correctly" It may say it is ok, yet it isn't ok. Nothing personal, yet that is some messed up reverse dns delegation. They do not have to alias anything other than authority. $ dig -x 12.148.244.151 ; <<>> DiG 9.2.4 <<>> -x 12.148.244.151 ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18524 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 3 ;; QUESTION SECTION: ;151.244.148.12.in-addr.arpa. IN PTR ;; ANSWER SECTION: 151.244.148.12.in-addr.arpa. 172800 IN CNAME 151.128/27.244.148.12.in-addr.arpa. 151.128/27.244.148.12.in-addr.arpa. 43200 IN PTR mail.cyways.com. ;; AUTHORITY SECTION: 128/27.244.148.12.in-addr.arpa. 43200 IN NS ns.cfmr.com. 128/27.244.148.12.in-addr.arpa. 43200 IN NS ns.cyways.com. 128/27.244.148.12.in-addr.arpa. 43200 IN NS ns2.cyways.com. ;; ADDITIONAL SECTION: ns.cfmr.com. 172800 IN A 12.148.244.131 ns.cyways.com. 86400 IN A 12.148.244.151 ns2.cyways.com. 86400 IN A 12.148.244.157 - rh -- Robert - Abba Communications Computer & Internet Services (509) 624-7159 - www.abbacomm.net
