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Internal (corporate) DNS reverse lookup returns multiple names

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geoffrie

MIS
Jun 2, 2009
3
US
Hello - Sort of a n00b question, at work we have a large network (30k devices in DNS), and use two Microsoft DNS and DHCP servers. We think the DHCP is set up wrong. Some DHCP ranges are served by one server, some by the other, and there may be some overlap. DHCP is used for PC's. Cleanup and maintenance of DNS has been a challenge.

Anyway - long story short - for many DHCP-assigned IP's when we do a reverse lookup (example - "nslookup 10.1.2.3" on a Linux box shows this the easiest), nslookup will return up to 50-60 different internal PC names. Each PC probably at some point in the last few years did have that IP address as its own, but obviously only one is valid at any one time. There are no external (Internet) hosts involved, and this DNS does not handle Internet-based hosts. All the hosts reported are internal. There is no intent to have this set up like this, it's a matter of crud building up over the years.

On Linux we can also see that the IP's that report the most hosts, report so many that nslookup has to switch from UDP to TCP because the UDP packet size is too small.

Does anyone else have this issue to this extreme ? Would this cause unintended negative consequences ? We have various system problems all the time. Cheers and thank you.
 
Negatory on scavenging. Thought for sure we had that enabled. I will ask the appropriate people here.

Thank you !
 
My mistake - we do enable scavenging, but we configure each zone individually, not global.
 
Make sure there are no errors in the event logs for your DNS servers. Even though scavenging is enabled, has it been running? Can you force it to run and check your logs to see if there are any errors?

good luck,
 
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