if i have the below ip 168.144.254.X and i would like to add a ptr record in amazon in the form of

X.254.144.168.in-addr.arpa what should be in the name field and what should be in the value field

i have a zone created with a name like mydomain.com which host the DNS records for my ip.

amazon wont let me add a value of X.254.144.168.in-addr.arpa in the name field

do i need to create a new zone for the ip in order to allow this?


If that address is your elastic IP, then you can submit a request for a reverse DNS record.

RDNS Request

However, I also find it odd that their own DNS service (Route 53) doesn't provide easy Reverse entries for IPs your account currently holds.

  • What can I do if it is a public IP, not Elastic IP? I have added a PTR record in Route 53, but it has not been propagated globally after 1/2 day. – quanta Mar 12 '14 at 22:41

The zone for reverse PTR records belong to whoever you got the IP address from. Contact them and have them add a PTR record for you.

They might be willing to delegate the PTR record to you. In that case you will need a zone like X-

  • Amazon provides the Route 53 DNS service /and/ the IP space, so you'd think they'd allow users to set reverse DNS entries. – Joel K Feb 12 '11 at 20:54
  • @Joel K: Show says this block belongs to Softcom Technology Consulting in Toronto. I did a random check for PTR records in the C block you have your IP in. There are security and trust issues with allowing users to set reverse DNS entries. Delegation is relatively new. Allowing direct updates risks giving access to at least a C block of addresses to every user in the block. Unlike A records, PTR record are expected to be relatively static. I just changed the PTR for my mail server and it was difficult (also restricted to a single record). – BillThor Feb 13 '11 at 4:38

You can't make a (legitimate) PTR for an ip address you do not control the reverse zone for. It would "work" if your resolver was configured to use the actual route 53 server (your NS records) for name resolution, but I doubt seriously those servers will allow recursive queries (I hope not). You need to ask the person responsible for that address's in-addr.arpa zone to create the PTR for you.

You can find this out with dig easily, though you may have to remove octets until you get an answer. This is for everything within 52.7, owned by AWS:

$ dig 7.52.in-addr.arpa ns

; <<>> DiG 9.9.5-4.3ubuntu0.2-Ubuntu <<>> 7.52.in-addr.arpa ns
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40013
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1

; EDNS: version: 0, flags:; udp: 512
;7.52.in-addr.arpa.     IN  NS

7.52.in-addr.arpa.  899 IN  NS  pdns1.ultradns.net.
7.52.in-addr.arpa.  899 IN  NS  x2.amazonaws.com.
7.52.in-addr.arpa.  899 IN  NS  x4.amazonaws.org.
7.52.in-addr.arpa.  899 IN  NS  x1.amazonaws.com.
7.52.in-addr.arpa.  899 IN  NS  x3.amazonaws.org.

;; Query time: 71 msec
;; WHEN: Thu May 07 14:26:50 CDT 2015
;; MSG SIZE  rcvd: 172

If the output is unclear about ownership, you can try the SOA record for the zone:

$ dig +short 7.52.in-addr.arpa soa
dns-external-master.amazon.com. root.amazon.com. 1033 3600 900 604800 900

The email address is dns-external-master@amazon.com. It is unlikely anyone follows these rules anymore, though.

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