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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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by:Carol Chisholm
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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.
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by:dns01
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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 .
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by:dns01
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DHCP server not shows the same IPs. i see only in DNS services.
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by:Carol Chisholm
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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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by:dns01
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ok i do.
sometimes i see in DHCP ,BAD ADDRESS shows
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by:dns01
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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?
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by:Carol Chisholm
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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.
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by:Carol Chisholm
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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?
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by:Carol Chisholm
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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)
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by:dns01
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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.
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footech earned 500 total points (awarded by participants)
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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/
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by:dns01
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i agree check scavenging settings ,actually they are default setting like 7 days etc, but i am sure there are some problems
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by:Carol Chisholm
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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?
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by:dns01
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Hi Carol,
Yes there was workstation2 ,i erased manually it ,lets see come back or not
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by:masnrock
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What Carol advised should work. One of the few other thoughts might be to try clearing out all of the DHCP leases.
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by:masnrock
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Best solution provided to question
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