DHCP/DNS Duplicate entries

[Greg Haslett]

Hi
I am new to microsoft DNS/DHCP implimentations.
We have win2k servers for DNS DHCP.
What is happening is duplicate entries in the DNS database. (two different A
records for the same IP address) The scavenge time is set to 7 days and the
DHCP lease time is set to 2 days.
I have tried to perform a scavange stale resoure records but it did not
remove the duplicate entries.
any ideas ???

 

[Herb Martin]

Are these dynamically registered? (Or manual?)

Same name, different IPs?

Consider using AD Integrated DNS but this shouldn't be happening
anyway.

 

[Greg Haslett]

Hi
Thanks for your reply

Everything is dynamically registered.

I get Different names with the same Ip address in the DNS MMC.
I am Using the Win2000 AD DNS product.

Thanks

 

[Deji Akomolafe]

This is normal, but a bit cumbersome to explain. Let me try briefly. DHCP
lease duration: 2days. DNS Scavenging: 7days. ComputerA (say a Laptop) wakes
up on Monday and requestes an IP. DHCP gives it 1.1.1.1, and registers this
in DNS as an A record( ComputerA 1.1.1.1). ComputerA's user goes on a 3-day
vacation and takes his laptop with him. ComputerB user comes in on Thursday
and requests an IP. DHCP server has now put 1.1.1.1 in its pool of available
IPs (because it's over 2 days and ComputerA has not requested a renewal). So
ComputerB now gets 1.1.1.1 and this gets registered in DNS (ComputerB
1.1.1.1). This is NOT a duplicate. It's a different record altogether. And
remember, DNS has NOT cleaned up the old record (ComputerA 1.1.1.1) YET
because it's NOT more than 7 days old (scavenging length).

I hope that does not confuse you too terrinly. Now, what do we do with the
info? Follow this thread here:
http://www.mail-archive.com/[email protected]/msg11017.html

and read more about Scavenging here:
http://www.microsoft.com/technet/pr...docs/standard/sag_DNS_und_AgingScavenging.asp

--
Sincerely,

Dèjì Akómöláfé, MCSE MCSA MCP+I
www.akomolafe.com
www.iyaburo.com
Do you now realize that Today is the Tomorrow you were worried about
Yesterday? -anon

 

[Greg Haslett]

Thank you very much for the info I will try the suggestions

 

[Herb Martin]

You know that isn't much of a problem really.

Consider having the DHCP server do all the registration and to remove
entries
when a lease expires.

The only issue is that if I try to contact machine "ONE" I might get the IP
currently
being used by "THREE", or "NINE".

If you have plenty of IPs....
Try making your leases LONGER rather than shorter, so that the DHCP server
will not give out the address of one machine to another so quickly.

 

[Jonathan de Boyne Pollard]

GH> any ideas ???

Have people release their DHCP leases before they remove their machines. (-:

 

[sharad]

To delete the old dynamically updated records, thorugh
scavenging they must be older than No.of days set in
"No refresh Interval" + No. of days set in "Refresh Inverval" (So if both
are set to 7 days, a record has to
be older than 14 days, to get remove.)

Further as explained by Deji and Herb, thse are not "DUPLICATE Recrods"
and will not harm, UNLESS , for some reason, reverse lookup has to be
performed, (e.g. a software requires to perform revrse lookp, for those
dynamically updated record.) So if you are not using any such a software,
it's no harm.

If you still do not want those many unnecessary records there, then enable
scavening, and set "No refresh Interval" and "Refresh Interval" to lower
values e.g. 2 days each.

Sharad