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DNS record updating

Posted on 2014-01-03
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Last Modified: 2014-01-09
Hi all,

2003 domain.

Have a dns question, I dont look at DNS enough to know exactly how to fix this issue.

The laptops on my network move between the local network and the VPN. When they connect to the VPN they record gets updated, but When I try and ping from the DC it still looks for the previous LAN address and times out?

Also, some machines haven't updated there record since march, I have deleted the record manually to see if this helps?

Realistically how quickly will this change take place?
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Question by:MJB2011
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by:Will Szymkowski
ID: 39754184
When a machine caches a record to a workstation the TTL is 3600 seconds which is 1 hour. This is how long the record is valid for before it is considered expired. Once the TTL has expired if the machine needs to communicate with that computer or device again it will query the DNS servers on the network for the most recent record. This process continues like this throughout.

If you know that a record has changed or is stale (expired) you can open a command prompt and type ipconfig /flushdns which will clear out all of the cached records on your machine. From there you will then query the DNS server directly to get the lastest record for that device or computer.

When you have static entries in DNS Manager these values dont change. Unlike DHCP host where their records can change all of the time due to new leases or if laptops are on different networks etc.

Will.
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Zephyr ICT earned 500 total points
ID: 39754195
I think the easiest approach is to implement scavenging on your DNS servers and implement DNS Dynamic Updates for the clients

Dynamic Updates: http://support.microsoft.com/kb/816592

Scavenging: https://blogs.technet.com/b/networking/archive/2008/03/19/don-t-be-afraid-of-dns-scavenging-just-be-patient.aspx?Redirected=true  and  http://technet.microsoft.com/en-us/library/cc759204(v=ws.10).aspx

That way the old/obsolete records in DNS will be deleted and the computers will always update the records when needed (when changes happen)
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by:Will Szymkowski
ID: 39754205
There is an option on the DHCP server under Scope>DNS tab "Always Dynamically Update Host A records and PTR records" make sure that this is enabled because it is not by default.

Will.
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by:Mahesh
ID: 39754615
Are you using DHCP for leasing IPs to clients in corporate network ?

You must create a dedicated user account and configure the DHCP servers with its credentials under the following circumstances otherwise DNS record updating will not work.

The DHCP server is configured to perform DNS dynamic updates on behalf of DHCP clients.
A domain controller is configured to function as a DHCP server. Without the dedicated user account, secure updates will not work.
The DNS zones to be updated by the DHCP server are configured to allow only secure dynamic updates.

Also you must set DNS scavenging in order to clean-up DNS at periodic interval as indicated by spravtek
http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_28306544.html

Mahesh
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