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I have an ubuntu server (server01.example.com) whose IPv4 address is 10.11.12.6, with a DNS server for the example.com domain at 10.11.12.2.

When I dig server01.example.com from cygwin on my Windows 7 box, I get the correct answer from the DNS server. When I nslookup 10.11.12.6, I get "server01.example.com". When I nslookup server01.example.com I get the correct response.

When I ping the server's IP address, I get a response. When I ping just "server01", I get a response.

It's only when I ping the server's fully-qualified domain name "server01.example.com" that I get "unknown host". Does anyone know what the heck could be happening?

P.S. - My real domain name is (obviously) not example.com, but the IP address are real.

Here's the wireshark capture of when I nslookup server01.example.com:

53  25.194795   server01.example.com    dc01.example.com        DNS 83  Standard query PTR 2.12.11.10.in-addr.arpa
54  25.194899   dc01.example.com        server01.example.com    DNS 114 Standard query response PTR dc01.example.com
55  25.197525   server01.example.com    dc01.example.com        DNS 92  Standard query A rabbit.example.com.example.com
56  25.197586   dc01.example.com        server01.example.com    DNS 156 Standard query response, No such name
57  25.198567   server01.example.com    dc01.example.com        DNS 92  Standard query AAAA rabbit.example.com.example.com
58  25.198633   dc01.example.com        server01.example.com    DNS 156 Standard query response, No such name
59  25.199559   server01.example.com    dc01.example.com        DNS 79  Standard query A rabbit.example.com
60  25.199663   dc01.example.com        server01.example.com    DNS 115 Standard query response CNAME app01.example.com A 10.11.12.6
61  25.200667   server01.example.com    dc01.example.com        DNS 79  Standard query AAAA rabbit.example.com
62  25.200736   dc01.example.com        server01.example.com    DNS 99  Standard query response CNAME app01.example.com
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Does nslookup server01.example.com return the correct IP address? –  Ansgar Wiechers Sep 11 '12 at 1:33
    
@Ansgar I logged on to get an answer your question and now pinging the FQDN works just fine. I haven't made any changes. I hadn't made any changes when I was first seeing the problem either. It simply went away. –  John Ruiz Sep 11 '12 at 19:31
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2 Answers

When you do an nslookup [ip address] what you are seeing is the ptr record. But when you do a ping it uses an A record.

You're doing three different tests:

  1. dig is returning the A record (but via cygwin, so it's not a good test of Windows lookup mechanism)
  2. nslookup is returning the PTR record
  3. ping is using Windows name resolution, which is a combination of hosts, netbios, dns and whatever other magical things might be installed.

Try doing an nslookup of nslookup server01.example.com and see what happens then.

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see my comment above. The problem mysteriously went away without me doing anything. So. Strange. –  John Ruiz Sep 11 '12 at 19:32
    
Okay, the behavior is back! When I nslookup server01.example.com, I get this: Server: dc01.example.com Address: 10.11.12.2 Name: server01.example.com Address: 10.11.12.6 Aliases: rabbit.example.com –  John Ruiz Oct 19 '12 at 21:49
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up vote 0 down vote accepted

This behavior is still happening to me off and on. This latest time, I found this technet thread and tried turning off the dnscache service, which fixed the issue.

This seems like a bug in the Windows DNS client/cache.

net stop dnscache
net start dnscache
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