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I have two DNS servers running. With internal addresses it is no problem to look them up both ways:


user@ns1:~$ man named.conf
user@ns1:~$ host vh01
vh01.example.de has address 192.168.180.4
user@ns1:~$ host 192.168.180.4
4.180.168.192.in-addr.arpa domain name pointer vh01.example.de.

But:


user@ns1:~$ host google.de
google.de has address 209.85.146.103
google.de has address 209.85.146.104
google.de has address 209.85.146.105
google.de has address 209.85.146.106
google.de has address 209.85.146.147
google.de has address 209.85.146.99
google.de mail is handled by 10 google.com.s9b2.psmtp.com.
google.de mail is handled by 10 google.com.s9a1.psmtp.com.
google.de mail is handled by 10 google.com.s9a2.psmtp.com.
google.de mail is handled by 10 google.com.s9b1.psmtp.com.
user@ns1:~$ host 209.85.146.103
Host 103.146.85.209.in-addr.arpa not found: 2(SERVFAIL)

I'd like to have something like:


user@ns1:~$ host 209.85.146.103 62.128.1.42
Using domain server:
Name: 62.128.1.42
Address: 62.128.1.42#53
Aliases: 

103.146.85.209.in-addr.arpa domain name pointer bru01s01-in-f103.1e100.net.

My server is configured to contact root dns-servers for unknown zones. I am assuming this working, since forward lookups are delegated if he himself doesn't know the answer. Why does it not delegate if it doesn't know about an IP address?

Any idea where I could have something wrong with my configuration?

As stated, I tried:


user@vh01:~$ dig +trace 103.146.85.209.in-addr.arpa ptr
; > DiG 9.7.3 > +trace 103.146.85.209.in-addr.arpa ptr
;; global options: +cmd
.                       518400  IN      NS      m.root-servers.net.
.                       518400  IN      NS      e.root-servers.net.
.                       518400  IN      NS      h.root-servers.net.
.                       518400  IN      NS      l.root-servers.net.
.                       518400  IN      NS      f.root-servers.net.
.                       518400  IN      NS      k.root-servers.net.
.                       518400  IN      NS      b.root-servers.net.
.                       518400  IN      NS      g.root-servers.net.
.                       518400  IN      NS      j.root-servers.net.
.                       518400  IN      NS      d.root-servers.net.
.                       518400  IN      NS      c.root-servers.net.
.                       518400  IN      NS      i.root-servers.net.
.                       518400  IN      NS      a.root-servers.net.
;; Received 244 bytes from 192.168.180.28#53(192.168.180.28) in 1 ms

arpa.                   172800  IN      NS      a.root-servers.net.
arpa.                   172800  IN      NS      g.root-servers.net.
arpa.                   172800  IN      NS      c.root-servers.net.
arpa.                   172800  IN      NS      i.root-servers.net.
arpa.                   172800  IN      NS      e.root-servers.net.
arpa.                   172800  IN      NS      k.root-servers.net.
arpa.                   172800  IN      NS      f.root-servers.net.
arpa.                   172800  IN      NS      m.root-servers.net.
arpa.                   172800  IN      NS      h.root-servers.net.
arpa.                   172800  IN      NS      d.root-servers.net.
arpa.                   172800  IN      NS      l.root-servers.net.
arpa.                   172800  IN      NS      b.root-servers.net.
;; Received 509 bytes from 192.58.128.30#53(j.root-servers.net) in 18 ms

in-addr.arpa.           172800  IN      NS      a.in-addr-servers.arpa.
in-addr.arpa.           172800  IN      NS      b.in-addr-servers.arpa.
in-addr.arpa.           172800  IN      NS      c.in-addr-servers.arpa.
in-addr.arpa.           172800  IN      NS      d.in-addr-servers.arpa.
in-addr.arpa.           172800  IN      NS      e.in-addr-servers.arpa.
in-addr.arpa.           172800  IN      NS      f.in-addr-servers.arpa.
;; Received 421 bytes from 198.41.0.4#53(a.root-servers.net) in 7 ms

209.in-addr.arpa.       86400   IN      NS      t.arin.net.
209.in-addr.arpa.       86400   IN      NS      u.arin.net.
209.in-addr.arpa.       86400   IN      NS      v.arin.net.
209.in-addr.arpa.       86400   IN      NS      w.arin.net.
209.in-addr.arpa.       86400   IN      NS      x.arin.net.
209.in-addr.arpa.       86400   IN      NS      y.arin.net.
209.in-addr.arpa.       86400   IN      NS      z.arin.net.
209.in-addr.arpa.       86400   IN      NS      dill.arin.net.
;; Received 200 bytes from 203.119.86.101#53(e.in-addr-servers.arpa) in 325 ms

146.85.209.in-addr.arpa. 86400  IN      NS      ns4.google.com.
146.85.209.in-addr.arpa. 86400  IN      NS      ns1.google.com.
146.85.209.in-addr.arpa. 86400  IN      NS      ns2.google.com.
146.85.209.in-addr.arpa. 86400  IN      NS      ns3.google.com.
;; Received 127 bytes from 199.212.0.63#53(z.arin.net) in 100 ms

103.146.85.209.in-addr.arpa. 86400 IN   PTR     bru01s01-in-f103.1e100.net.
;; Received 85 bytes from 216.239.36.10#53(ns3.google.com) in 5 ms

It looks good to me, but why does


user@vh01:~$ host 209.85.146.103
Host 103.146.85.209.in-addr.arpa not found: 2(SERVFAIL)

fail? But does not, if I query an address handled by my own server?


user@vh01:~$ host 192.168.180.4
4.180.168.192.in-addr.arpa domain name pointer vh01.example.de.
share|improve this question
    
Try dig +trace 103.146.85.209.in-addr.arpa ptr to try and find out where it's failing. –  Hyppy May 19 '11 at 14:41
    
It seems not to fail at all –  tps800 May 19 '11 at 15:27
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1 Answer

If you only have one public IP address, you will have to ask your ISP to create the PTR record in their reverse DNS.

If you have a range of public IP addresses, your ISP will need to provide a reverse DNS forward to your DNS servers for the PTR records, and you need to establish a reverse DNS zone for these IP addresses. This can be done either as individual CNAME records (for less than 256 IP addresses) or as a complete subnet forward.

share|improve this answer
    
I may be reading it wrong, but I think he's trying to wonder why PTR lookup is failing to resolve anything from his server, since the failure he's posting is for google.de's address. –  Hyppy May 19 '11 at 15:29
    
That is not my problem. I do know about this fact. It's my own server not handling ptr lookups, instead handling me the servers DNS-name giving SERVFAIL for all not local addresses. I'd like it to give back what everyone expects: the name, not an error. –  tps800 May 19 '11 at 15:45
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