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Originally Posted by Rayc I wonder if anyone has any idea to solve this problem yet - cos I am having this problem as well: the fixed ip address not ...
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    Problem in assigning DHCP fixed address to clients


    Quote Originally Posted by Rayc View Post
    I wonder if anyone has any idea to solve this problem yet - cos I am having this problem as well: the fixed ip address not being updated on DNS server. From the man page I can see that there is a setting of "update-static-leases" is for this purpose. However it still not working properly even I set it to "on". Anyone help ?
    Thanks.
    I am also having the same problem. Several Windows computers (XP and 8.1) don't pick up the static address assigned to their hardware MAC address. They get one of the dynamically assigned range addresses instead. I can't figure out if this is something in the Windows networking configuration on each Windows computer or in the dhcpd.conf file.

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    Super Moderator Roxoff's Avatar
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    Sorry, but I split your post off that old thread onto its own - things may have moved on quite a long way since 2006...

    Anyhow - onto helping you. DHCP clients of all kinds have a tendency to request the same address when they renew their lease after previously being assigned an address. This allows continuity and predictability when the system is all working find, but can be a pain in the rear when it doesn't. There are a few tricks you could try to force the system to hand out the IP address you want.

    On the Windwos computer the dos-prompt command 'ipconfig /renew' should cause your DHCP subsystem to request its address again immediately. If that doesn't get your computer on the address you want, then first up: check you typed your MAC address in correctly, if not - fix it and retry the renew statement (don't forget to restart your DHCP service before you try the renew command).

    If it's still not doing it right, you need to force a different address by excluding the currently assigned one temporarily from the pool of those available to your DHCP server. You can do this by updating the range available in the DHCP config and restarting the service. Once this is out of the available range, renew the lease on your Windwos PC, it'll ask for the same IP but it's no longer available and hence it will be allocated a new one through the normal process, i.e. the DHCP server should check the static assignments before trying to provide an IP address from the pool. If you try this, don't forget to reset the DHCP range again (and restart your DHCP server) before putting everything away.
    Linux user #126863 - see http://linuxcounter.net/

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    Quote Originally Posted by Roxoff View Post
    Sorry, but I split your post off that old thread onto its own - things may have moved on quite a long way since 2006...

    Anyhow - onto helping you. DHCP clients of all kinds have a tendency to request the same address when they renew their lease after previously being assigned an address. This allows continuity and predictability when the system is all working find, but can be a pain in the rear when it doesn't. There are a few tricks you could try to force the system to hand out the IP address you want.

    On the Windwos computer the dos-prompt command 'ipconfig /renew' should cause your DHCP subsystem to request its address again immediately. If that doesn't get your computer on the address you want, then first up: check you typed your MAC address in correctly, if not - fix it and retry the renew statement (don't forget to restart your DHCP service before you try the renew command).

    If it's still not doing it right, you need to force a different address by excluding the currently assigned one temporarily from the pool of those available to your DHCP server. You can do this by updating the range available in the DHCP config and restarting the service. Once this is out of the available range, renew the lease on your Windows PC, it'll ask for the same IP but it's no longer available and hence it will be allocated a new one through the normal process, i.e. the DHCP server should check the static assignments before trying to provide an IP address from the pool. If you try this, don't forget to reset the DHCP range again (and restart your DHCP server) before putting everything away.
    Thanks.

    My problem seemed to arise from several different issues. The first was that I was editing the dhcpd.conf in /etc/dhcp3/, instead of in /etc/dhcp/, so restarting the isc-dhcp-server wasn't reflecting any changes I made. I'm not sure why I have a /etc/dhcp3/ directory, unless it was created from some other installation. Secondly I tried the Windows commands: "ipconfig /release" and "ipconfig /renew", which still gave me the same static ip address (incorrect old address) from before. After rebooting the Windows computer isc-dhcp-server did finally give me the updated correct static ip address.

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    From the linux side of things, is there a way to flush all the dhcp leases, so that all the computers on the network will be forced to re-aquire new leases?

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    Super Moderator Roxoff's Avatar
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    I'm not aware of any - it'd involve sending an instruction to each DHCP client asking them to renew, and that isn't all that simple.

    It shouldn't really be a problem, though - normally you'd have the lease time on IP addresses set to 1 or 2 hours, so after this they'd all have renewed anyway. It is configurable, of course, so you might have set it longer.
    Linux user #126863 - see http://linuxcounter.net/

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