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windows 2000 DNS Records

I would like to know in which situations Windows DNS gets 2 records for the same client machine(XP)? and how to avoid this to happen?


thanks
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jskfan
Asked:
jskfan
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6 Solutions
 
BudDurlandCommented:
Workstation is configured to register it's connection in DNS (look at tcp/ip properties, advanced).  It's DHCP lease expires, and it gets a new address.
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jskfanAuthor Commented:
I understand,

but I have 2 xp clients now that have the same IPs, the same DNS records
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BudDurlandCommented:
I'm sorry, I thought you had the same PC registering two IP addresses.  Two clients registering the same IP might be caused by a disagreement between one of the clients and the DHCP server about the IP lease. I.E. the DHCP server thought the lease had expired, and gave the IP address to a different client
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jskfanAuthor Commented:
how do you solve this?
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arnoldCommented:
First you should check your DHCP configuration to make sure the IPs that you are referencing are in the DHCP pool.  Then you should check the clients and make sure that one is not setup with that IP as a static IP or make sure that you did not configure this IP as a reserved IP.

I suspect that this is what is going on.

however, if both systems are configured to obtain an IP via DHCP, on one of the system run ipconfig /release_all to release the IP.  Then ipconfig /renew.  This should trigger the request for a new IP.

Disabling and enabling the network connection will do the same.
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giltjrCommented:
Before you check your DHCP configuration, check the workstations to make sure they are both configured for DHCP.  We have had this issue because somebody configured their computer with a static IP address.

Generally two computers on the same network with the same IP address will also cause other problems if they are both attempting to connect to the network at the same time.

Do they really have the same IP addres, or are they just registred in DNS?  Are their two A records with the same IP address or is there a single PTR record with mutliple host names.  IIRC Windows does NOT remove PTR records.  We have had a single PTR record with 10 host names.
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bkoehler-mprCommented:
The DHCP issue can be resolved by enabling conflict detection, which causes the DHCP server verify the address isn’t in use before issuing it.

Start the DHCP MMC
Right click your DHCP server, Properties
Advanced tab
Increase "Conflict detection attempts" from 0 (default) to 1.
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rindiCommented:
Sometimes this can also happen if your switch where the workstations connect to has a bad port, or the NIC's on the workstation don't have the corresponding settings of the ports on the Switch. If the NIC is set to "Autosense" for speed and duplex mode, the same should be true for the port on the switch (if it is manageable). If the NIC is set to 100MB/FD, the port on the switch should have the same settings.
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jskfanAuthor Commented:
workstations are good, when I run ipconfig /release the renew they get a proper IP address.

example computer1 : 122.1.1.40 but in DNS it's 122.1.1.10
             computer2:  122.1.1.10 and in DNS it's 122.1.1.10 (this one is correct)

do I have to manually delete the A record? and this happens to many of the workstations.
 I checked aging and scavanging and it set up to its default.

I don't know how to solve and prevent this problem to happen.


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rindiCommented:
Are you using the windows 2k server as dhcp server or are you using another box for that? If possible, disable any other DHCP server and use your windows server to provide the DHCP service.
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jskfanAuthor Commented:
yes we use windows 2000 server as DHCP
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prashsaxCommented:
You need to check if some other DHCP erver is not running.

A simple way to do is just disable your main DHCP server and try an acquire IP address on one of the client machine.


Their could be due to one more reason.

If you subnet range is not enough of is neck n neck with the number of clients.

Suppose you have 200 clients and your IP pool have 201 ip addresses.

Then DHCP server will not be able to assign same ip address to the client machine again and again.

Now what happens is that machine will register its IP address with DNS.
Then next day it will again register different IP address but old one is not deleted.

So in reality your DNS record shows two PC with same IP, but if you go to each PC and check manually they will have different IP addresses.


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jskfanAuthor Commented:
prashsax ,

I can'I disable now a dhcp server during production time.

<<<Suppose you have 200 clients and your IP pool have 201 ip addresses.>>>

do you mean I have to setup the IP pool accordingto the clients machine that request IP? if so I will have to change the pool everytime I add or remove a computer.


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bkoehler-mprCommented:
Make sure Dynamic DNS is configured both on the DNS and DHCP server, and that your DHCP server has conflict detection enabled.

From: http://www.microsoft.com/technet/community/columns/cableguy/cg0401.mspx

Windows 2000 DNS Server

To enable DNS dynamic update on a Windows 2000 DNS server:
1.Click Start, point to Programs, point to Administrative Tools, and then click DNS.
2.In the console tree, click the appropriate zone in Forward Lookup Zones or Reverse Lookup Zones.
3.On the Action menu, click Properties.
4.On the General tab, verify that the zone type is either Primary or Active Directory-integrated.
5.If the zone type is Primary, in the Allow dynamic updates? list, click Yes.
6.If the zone types is Active Directory-integrated, in the Allow dynamic updates? list, click either Yes or Only secure updates, depending on whether you want DNS dynamic updates to be secure.

Windows 2000 DHCP Server

To configure DNS dynamic update for a Windows 2000 DHCP server:

1.Click Start, point to Programs, point to Administrative Tools, and then click DHCP.
2.In the console tree, click the appropriate DHCP server or a scope on the appropriate DHCP server.
3.On the Action menu, click Properties.
4.Click the DNS tab.
5.To enable DNS dynamic update for DHCP clients that support it, select the Automatically update DHCP client information in DNS check box. This option is enabled by default.
6.To enable DNS dynamic update for DHCP clients that do not support it, select the Enable updates for DNS clients that do not support dynamic updates check box. This option is disabled by default.
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rindiCommented:
"do you mean I have to setup the IP pool accordingto the clients machine that request IP? if so I will have to change the pool everytime I add or remove a computer."

No, but you should have the pool large enough to accomodate for more users than you have, or at least large enough that there are allways enough addresses available for all the users you expect to be onsite at one time. Also reduce the TTL time (Time To Live) so that leases are freed once they aren't used anymore.
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jskfanAuthor Commented:
clients they get the new IP from DHCP, the problem is they can't update it in the DNS.

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bkoehler-mprCommented:
Step 1
Make sure your DNS server is configured to allow dynamic updates (see above)

Step 2
Make sure your DHCP server is configured to supply dynamic updates (see above)

Step 3
Enable DHCP Conflict Detection if machines keep getting the same IP (see above)

Step 4
Report back any errors you see while implementing steps 1 - 3.
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prashsaxCommented:
if you are sure that clients are not updating the the DNS records then do this.

Allow unsecure updates on DNS. (Just for Test).

Then either make a script which will do :

ipconfig /registerdns

this should update the record.

You should always have more IPs in your pool then the number of machines in the network.
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jskfanAuthor Commented:
Let me give you the records details in DNS

computer1   host(A)     122.1.1.40
Computer2  Host(A)     122.1.1.40

**Notice: they both have the same IP

==============================

122.1.1.40         Pointer(PTR)  Computer1
122.1.1.40         Pointer(PTR) Computer55
122.1.1.40         Pointer(PTR) Computer66

**Notice: the same IP is for 3 different machines, computer1 is on the top and computer 2 is not there at all

===============================

122.1.5.56     Pointer(PTR) Computer2

**Notice: computer 2 has a different IP and this is the IP I get when I tun Ipconfig from the workstation itself. So this should be the right one.

===============================




 
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giltjrCommented:
I forget what the term is but Windows DNS, for A records only, has some type of "scavange" feature where it will delete what it beleives are invalid A records.  You may need to enable this.

That I am aware of there is no such feature for PTR records.  Our Windows Admins finaly turned off autocreation of PTR records because of the mess is created.
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jskfanAuthor Commented:
Aging and scavenging is already on.
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jskfanAuthor Commented:
What is the process of resolving this issue?


computer1   host(A)     122.1.1.40
Computer2  Host(A)     122.1.1.40

**Notice: they both have the same IP

==============================

122.1.1.40         Pointer(PTR)  Computer1
122.1.1.40         Pointer(PTR) Computer55
122.1.1.40         Pointer(PTR) Computer66

**Notice: the same IP is for 3 different machines, computer1 is on the top and computer 2 is not there at all

===============================

122.1.5.56     Pointer(PTR) Computer2

**Notice: computer 2 has a different IP and this is the IP I get when I tun Ipconfig from the workstation itself. So this should be the right one.

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giltjrCommented:
PTR records you will need to delete.  Do both of the A records have their own TTL?
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jskfanAuthor Commented:
TTL is 1 day
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