Question regarding dchp renewals

royal · August 2006

If I had a scope that defined a DNS server of 192.168.0.2 and I had to change the ip address for the dns server in the scope, how do I get the clients to update it? I know that at 50% and 75% of the lease they'll try to automatically renew, as well as when their computer boots up. If it contacts the dhcp server on lease renewal, will it automatically update and detect the dns ip change and update its dns settings on the client side?

agustinchernitsky · August 2006

Try and remove the lease from the server... They won't find it every time they turn on the PCs, so they should get a new Lease... I think

RTmarc · August 2006

After you've changed it in the DHCP scope settings the client will not update until they renew their lease. Once the clients start renewing their lease they will get the new settings. Unless you manually update the clients that have just obtained a new lease before the changes were made, they will not be updated until ther lease is at 50%.

sprkymrk · August 2006

agustinchernitsky wrote:

Try and remove the lease from the server... They won't find it every time they turn on the PCs, so they should get a new Lease... I think

I don't believe this works (not because I am smart, but because I tried it once). The client still needs to "release" the address whether or not the server keeps track of it.

I wrote a script that enumerates a list (created by exporting the DHCP data) and remotely performs a "renew" on ipconfig. It will temporarily interrupt their network connection (lasting about 2 seconds) but will renew their IP information from the DHCP server immediately.

agustinchernitsky · August 2006

Hello sprkymrk,

Well, it was just an idea... I didn't try it... glad you did

By the way, your script looks MS solution too: http://support.microsoft.com/kb/154488/EN-US/

Maybe GPOs and batch files are the solution after all! LOL!

blargoe · August 2006

Something like what sprkymrk suggested is the only way to force scope changes to immediately take effect on the client end without manually release/renew.

sprkymrk · August 2006

agustinchernitsky wrote:

Hello sprkymrk,

Well, it was just an idea... I didn't try it... glad you did

By the way, your script looks MS solution too: http://support.microsoft.com/kb/154488/EN-US/

Maybe GPOs and batch files are the solution after all! LOL!

Hey, you're good at finding this stuff agustinchernitsky.
The only problem I see with the MS script is that I think if the user is not an admin he cannot relese and renew his IP. Haven't I seen an "access denied" on that command when not logged in as an admin? Anyone know for sure?

Slowhand · August 2006

If I'm not completely out of my mind here, you can force all the clients to renew their IP address information by restarting them, which I believe you can do from the server(?)

blargoe · August 2006

Well, technically you could remotely shut down all of the PC's using something like shutdown -i... that would be awfully extreme though

Slowhand · August 2006

"Attention all users, this is your network admin speaking. Due to a change in the network infrastructure, your computers will be shutting down. . . now." *Click* "That is all."

RTmarc · August 2006

You can force the shutdowns with the command line, as stated previously, but the remote command is -m \\[computername]

. Administratively speaking, the best thing to do is just send out an email to people affected asking them restart their machines when the leave work in the afternoon or when the come in first thing in the morning if you make it afterhours; granted the change is non-critical then it's time to enact the help desk to go out and reboot everyone or renew IP.

blargoe · August 2006

shutdown -i is the gui. I like gui's

Danman32 · August 2006

Of course you could support the original IP for DNS until all the leases expire and the option specs are renewed.
Support the original IP by leaving that server remaining up for a while, or transfer the IP to the new DNS server as a secondary IP, or an existing member server running DNS with no zones but unconditional forwarding to the new server. Last option I would say is the best idea since it can't cause DS/AD issues with dual IPs on a DC.

Question regarding dchp renewals

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