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Windows Thread, forcing dhcp renew across network in Technical; I did this - if we are on about changing the ip range on a network - and although all ...
  1. #16
    tarquel's Avatar
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    Re: forcing dhcp renew across network

    I did this - if we are on about changing the ip range on a network - and although all the machines had changed their ip, they were still looking for the old DNS IP [as the server had changed IP too naturally].

    I've had to wipe them all - as i've said in another topic [no time to link right now]

    Just so ya know - hope u dont have that problem lol

    Regards
    N.

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    Re: forcing dhcp renew across network

    In the DHCP Server Options > advanced tab, microsoft options > there's an option to release DHCP on shutdown

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    Re: forcing dhcp renew across network

    in end what did was download psexec and create a batch with

    ipconfig /reelease
    ipconfig /renew
    in it caled it test.cmd

    then in second batch file put called redo.cmd added: -

    rem @echo off
    cls
    net use s: \\%1\c$
    if exist s:\test.cmd goto endfile
    copy test.cmd s:\ /Y
    net use s: /delete

    psexec \\%1 c:\test.cmd

    :endfile
    net use s: /delete


    once that was got list of w/s in excel in column b and then word redo in column a

    then in c col did formula =A2&B2&C2 copies all way down then copies col c into notepad saved as do.cmd

    ran do.cmd and it is just working through the list

    Russ

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    tarquel's Avatar
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    Re: forcing dhcp renew across network

    nice one russ

    nice 'n' simple script

    Nath

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    Re: forcing dhcp renew across network

    Sounds like fun!

    First, make sure you reduce the DHCP lease time on your new setup - 3 days is more usual to jelp avoid problems.

    Exact behaviour of DHCP depends on the verisons of client and server (although it is supposed to be a standard)

    Basically, if I remember correctly, clients will try to get a renewal after half the lease time has expired. If they don't get one, they will carry on with the old IP until the leae runs out.

    However on boot up they should try and check their lease with the DHCP server they got it from, and hope for an acknowledgement (ACK).

    Unless you plan on waiting 30 days (I suspect not) you need to get this boot up process to deliver a negative acknowledgement (NACK)

    To do this you first need to make sure that your DHCP server knows that these addresses are no longer valid. By the sound of it you have done that.

    The second part is to make sure that machines booting up with the old IP address can still access the DHCP server. If they can't, they will just carry on withthe old IP address.

    It sounds as if part of the IP address changes you have made as removed the valid network route from PCs with old numbers to the DHCP server with an old number. Have you change the whole IP subnet and re addressed the DHCP server?

    If that is the case, you have 2 options.
    1. run arund all the machines and renew manually :-)
    2. Set the DHCP server up as dual homed - with two IP addresses (old and new) and set to cancel the old scope and issue addresses on the new scope. Then reboot PCs and you are away. Once they are all done, don't forget to tidy up the DHCP server.

    Hope that helps.



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