When modifying DHCP scope to make a change to DNS servers, will AD users get the new changes when they log off and back on to their systems?

Posted on 2013-09-23
Medium Priority
Last Modified: 2013-09-24
Our DHCP scope lease time is set for 24 hours. I am working on a project which requires me to point all DNS settings for our users to a new DNS server. I plan to have the DHCP change user’s DNS settings to point to a different DNS server once I make the modification in the DHCP scope. I plan to make the change on a Friday after business hours, so that when users come back Monday, they will have the new DNS settings.  My question is if I change the DNS, and if I use my workstation to test it by rebooting my workstation shortly after the change, would it pick up the new DNS settings even though the lease time in DHCP is set for 24 hours? After making the change in DHCP, do I need to enforce anything or should the change take affect instantaneously? Once I make this change, I need to test it, so will rebooting my system after the change take effect instantaneously?
Question by:jaedenone
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Expert Comment

by:Emmanuel Adebayo
ID: 39516637
Yes, the list of the new DNS servers will be made available to the client when the log on.
IP addressing information is leased to a client, and the client is responsible for renewing the lease. By default, DHCP clients try to renew their lease when 50 percent of the lease time has expired. To renew its lease, a DHCP client sends a DHCPRequest message to the DHCP server from which it originally obtained the lease.



Author Comment

ID: 39516862
Just to confirm, If users reboot there machine, there IP address will remain the same, but there DNS will change right? I don't care if IP remains the same, but just so long as there DNS change after they log off and back on or reboot, when after I make my changes for DNS on the DHCP scope. I understand that there IP address will remain the same because there is a 24 hr lease we put on that, but that is fine.  Can you confirm?
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Assisted Solution

by:Emmanuel Adebayo
Emmanuel Adebayo earned 1000 total points
ID: 39516899
The IP might not remain the same this will depend on if the dhcp assign the same ip address when the system is requesting ip, but definitely the dns settings will be pushed to the clients.

LVL 17

Accepted Solution

vivigatt earned 1000 total points
ID: 39517882
But usually, the IP address will remain the same, since the client records its previous IP address in the registry and asks for it again as its "preferred IP address". However, there is no guaranty that this is the address the client will actually get. If the lease hasn't expired, there are great chances that the client will get the same address again.
However, using a different address should not cause any issue.
And yes, the DNS servers will be updated when the client reboots or when the lease is renewed.
If your clients are members of an AD domain, remember that the first DNS in the list must be a domain controller.

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