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Windows server Active Directory Server and DNS server

Posted on 2016-10-03
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Last Modified: 2016-10-25
DNS service shows many computer has the same IP .example ,i see on my dns server COMPUTER1 and COMPUTER2 has the same ip addresses (DHCP addresses),I use DHCP server on my network  and no STATIC IP.
why they get the same IPs ?

Please help
Thanks
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Question by:dns01
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16 Comments
 
LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826658
Your example is not visible.

Are you sure you have only 1 DHCP server?
On COMPUTER1 run IPCONFIG/ALL and make sure your DHCP server has the correct address.

You do not tell us what versions you are using.
0
 

Author Comment

by:dns01
ID: 41826666
yes i have only one dhcp server which is on AD(Dns) server.

in DNS i see some of computer (hostname) are the same IP. I ping and get answer from computer which has the same IPs.

Active Directory server(DNS+DHCP) is windows 2008 standard .
0
 

Author Comment

by:dns01
ID: 41826669
DHCP server not shows the same IPs. i see only in DNS services.
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LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826681
Perhaps you have another DHCP server (a firewall or router)

If you run IPCONFIG/ALL from a command prompt on a computer that has a bad IP you can see the IP address of the DHCP server
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Author Comment

by:dns01
ID: 41826684
ok i do.
sometimes i see in DHCP ,BAD ADDRESS shows
0
 

Author Comment

by:dns01
ID: 41826697
I do not understand something  , how can 2 x DHCP server at the same network and the both are same IP range.?

I think somehow DNS zone Problem  or?
0
 
LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826706
DHCP servers are very simple. Many routers, telephone systems and switches have built in DHCP servers.
You can get two by mistake and it will cause problems

Each COMPUTER will tell you the IP address of the DHCP server it is using if you run the command (Start - Run - CMD) IPCONFIG/ALL

Then you can check the IP address of the DHCP server. If is of a different address to your main DHCP server you must find the device that is the false DHCP server and stop it giving addresses.
0
 
LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826708
It could also be a DNS zone problem, but DNS servers do not give addresses to computers.
Have you checked on the computers if they have the IP address that is in the DNS?
0
 
LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826712
You must check the COMPUTERS to see what address they REALLY have,
Then check if the address is the same as the DNS (DNS is only recording information sent from the computer)
0
 

Author Comment

by:dns01
ID: 41826776
Actually problem is :

in DNS Record shows:

workstation01 192.168.100.119
workstation02 192.168.100.119

and both pingable.

in DHCP(range 110-220):

workstation01 192.168.100.119
no workstation02 there.
0
 
LVL 40

Accepted Solution

by:
footech earned 500 total points (awarded by participants)
ID: 41826834
Depending on your settings, it's likely that old DNS records are not being removed.  You'd want to check which settings are configured in your DHCP server options for the DNS tab, and for the DNS server scavenging settings along with dynamic update settings which are per zone.

I'd suggest these links as good reading.
https://blogs.technet.microsoft.com/networking/2008/03/19/dont-be-afraid-of-dns-scavenging-just-be-patient/
https://blogs.technet.microsoft.com/askpfe/2011/06/03/how-dns-scavenging-and-the-dhcp-lease-duration-relate/
http://blogs.msmvps.com/acefekay/2009/08/20/dhcp-dynamic-dns-updates-scavenging-static-entries-amp-timestamps-and-the-dnsproxyupdate-group/
0
 

Author Comment

by:dns01
ID: 41826841
i agree check scavenging settings ,actually they are default setting like 7 days etc, but i am sure there are some problems
0
 
LVL 16

Expert Comment

by:Carol Chisholm
ID: 41826955
So there was a workstation2 before? it is now removed and the DNS entry has not gone?
If you delete it manually does it return?
0
 

Author Comment

by:dns01
ID: 41827812
Hi Carol,
Yes there was workstation2 ,i erased manually it ,lets see come back or not
0
 
LVL 28

Expert Comment

by:masnrock
ID: 41832412
What Carol advised should work. One of the few other thoughts might be to try clearing out all of the DHCP leases.
0
 
LVL 28

Expert Comment

by:masnrock
ID: 41858240
Best solution provided to question
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