To check that a given host has the reverse DNS setup correctly, you could:

host -t ptr 209.85.229.99

99.229.85.209.in-addr.arpa domain name pointer ww-in-f99.1e100.net.



or to do the same thing with dig:

dig -x 209.85.229.99

; <<>> DiG 9.6-ESV-R3 <<>> -x 209.85.229.99

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 41932

;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:

;99.229.85.209.in-addr.arpa. IN PTR

;; ANSWER SECTION:

99.229.85.209.in-addr.arpa. 79482 IN PTR ww-in-f99.1e100.net.

;; Query time: 1 msec

;; SERVER: 87.117.198.200#53(87.117.198.200)

;; WHEN: Wed May 11 12:36:25 2011

;; MSG SIZE rcvd: 77



Do not specify any server to query, and it'll do it via your host's resolver, and prove that things are working across the 'net

You can try using a remote DNS server to check the reverse lookup. You can do this by providing the hostname or IP address of a DNS server to your query using nslookup or host.

bigwig:~ jimh$ host 209.85.143.104 8.8.8.8

Using domain server:

Name: 8.8.8.8

Address: 8.8.8.8#53

Aliases:

8.8.8.8 is a Google DNS server that allows recursive lookups that often comes in useful. It is handy to check if your DNS record has propagated.

You can also use:

dig -x +trace +all 123.123.123.123

and this will take you through, step-by-step, the queries that are made as it contacts the root DNS servers downwards and the replies you receive. If there are issues, you can use this to find out at which point you went astray.

Dig can be really verbose and helps check if it's a live result and not cached. Note that the /24 IP range is written backwards in essence for the in-addr.arpa notation below.

dig +multiline @PRI.AUTHDNS.RIPE.NET 123.123.123.in-addr.arpa NS

So if your example range was: 123.456.789.0/24 then the in-addr.arpa notation would be 789.456.123.in-addr.arpa above.

I'm not sure about a list of NSs with RIPE but the one above seems correct,