We have the following problem with our Windows AD DNS Servers which is in turn causing intermittent issues on our clients:
On one of our AD DC/DNS servers (Pluto) 2k3R2, we can ping an internal based host using it's full external hostname (docs.is.com.au) and it will resolve back to 192.168.1.210 and reply to pings - great!
On another AD DC/DNS server (Venus) 2k8R2, we ping the same hostname and it resolves to it's external internet address of 126.96.36.199 and cannot be pinged due to the firewall doing what it is meant to do and blocking it.
On both servers, if I was to ping docs (without the full domain name) it resolves to the correct internal IP address.
Why would one DNS Server be finding the internal IP correctly and the other not and resolving to the External IP?
Our AD Domain: im.is.com.au
Inside of this forward lookup zone the name docs is a CNAME pointing to sharepoint.im.is.com.au
We also have a forward lookup zone of is.com.au in which docs is a CNAME also pointing to sharepoint.im.is.com.au
Doing an NSLookup on Venus the host that does not give the correct ping address results in the following:
>nslookup docs.is.com.au venus 188.8.131.52.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa primary name server = cha-na.telstra.net responsible mail addr = root.cha-na.telstra.net serial = 20081105 refresh = 3600 (1 hour) retry = 900 (15 mins) expire = 3600000 (41 days 16 hours) default TTL = 3600 (1 hour) Server: UnKnown Address: ::1 Name: sharepoint.im.is.com.au Address: 192.168.1.210 Aliases: docs.im.is.com.au
Doing a NSLookup on Pluto which does give the correct address:
>nslookup docs.is.com.au pluto Server: pluto.im.is.com.au Address: 192.168.1.220 Name: sharepoint.im.is.com.au Address: 192.168.1.210 Aliases: docs.is.com.au
It seems like this second forward lookup zone is the problem but I am not sure how or where I should be looking.
If any more info is required, please let me know!
Similar posting here: Windows Server 2008 - Strange DNS resolution between clients and server but the clients and servers are all using internal AD DNS servers, no external DNS Servers are setup on the nics.
Both AD DNS servers have ISP name servers setup in the Forwarders tab with 'Use root hints' UNCHECKED.
The servers do not have any ISP/Google/Other external DNS Servers listed on their network adapters, nor do the clients - they are all pointing to the internal servers or in the case of the DNS Servers are uisng 127.0.0.1 as their alternates.
Results of NSLookup on client - after possible fix implemented (see comments)
>nslookup docs.im.com.au venus Server: venus.im.is.com.au Address: 192.168.1.217 Name: sharepoint.im.is.com.au Address: 192.168.1.210 Aliases: docs.is.com.au >nslookup docs.is.com.au pluto Server: pluto.im.is.com.au Address: 192.168.1.220 Name: sharepoint.im.is.com.au Address: 192.168.1.210 Aliases: docs.is.com.au