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#104652 - 2003-09-15 03:27 PM Off topic: Force DHCP Server to assign new IP to client?
Allen Allen KiX Supporter Registered: 2003-04-19 Posts: 4562 Loc: USA	We need to assign a different dhcp assigned address to a client PC. If I do ipconfig /release and then ipconfig /renew on the client, the DHCP server does as expected, and reassigns the original address to the client. I do not have access to the DHCP server, so a reservation is not an option. Anyone have any ideas?
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#104653 - 2003-09-15 03:36 PM Re: Off topic: Force DHCP Server to assign new IP to client?
Radimus Radimus Moderator Registered: 2000-01-06 Posts: 5187 Loc: Tampa, FL	replace the NIC. DHCP servers assign addresses by MAC address. If you do not have access to the DHCP server, then you can only remove the PC and let it's lease expire _________________________ How to ask questions the smart way <-----------> Before you ask
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#104654 - 2003-09-15 03:41 PM Re: Off topic: Force DHCP Server to assign new IP to client?
Allen Allen KiX Supporter Registered: 2003-04-19 Posts: 4562 Loc: USA	Yeah, thought of that too, but unfortunately it's an integrated NIC. I guess if worse came to worse, I could just stick another NIC in the PC. Thanks for the idea. Any others?
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#104655 - 2003-09-15 09:59 PM Re: Off topic: Force DHCP Server to assign new IP to client?
kholm kholm Korg Regular Registered: 2000-06-19 Posts: 714 Loc: Randers, Denmark	Have you tried: 'ipconfig /release' 'Reboot' The reboot SHOULD give you a new IP-adr based on the correct vlan/MAC-adr. I don't really belive this will work, beacuse: I have had some strange results in WINS/DNS, when using a different name for a workstation that is reenroled to the domain on a different subnet or with a new name. DHCP 'knows' the ws in advance by MAC-adr, so the old lease/IP-adr is used even for a different subnet. Even worse, sometimes WINS is not updated correctly, and other times DSN is not updated correctly. You might even have the ws registrered twice in DHCP with different ws-names, but registrered by same MAC/IP The bullitproof method for me is to remove all entries in DHCP/WINS/DNS. I know you can't do that, so this is just a suggestion for a trial an error method, might work/might not. Maybe someome with greater insight in the naming protocols can add to this. -Erik
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#104656 - 2003-09-15 10:23 PM Re: Off topic: Force DHCP Server to assign new IP to client?
painless painless Lurker Registered: 2003-04-07 Posts: 4	You could try spoofing the MAC address and doing a renewal. See: http://www.klcconsulting.net/smac/terms_of_use_mirror1.htm for a ready made tool to do this. Never actually tried this under Windows, so use at your own risk.
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#104657 - 2003-09-15 10:46 PM Re: Off topic: Force DHCP Server to assign new IP to client?
kholm kholm Korg Regular Registered: 2000-06-19 Posts: 714 Loc: Randers, Denmark	painless, welcome back (I thougt you died in MAS*H Korea), That would have been my second suggestion: Change the MAC-adr by overriding the hardcoded address by a software set address (EPROM). Somewhere deep in my private QA, i have a reference to legal private MAC-Adr's -Erik
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#104658 - 2003-09-16 01:15 AM Re: Off topic: Force DHCP Server to assign new IP to client?
Les Les KiX Master Registered: 2001-06-11 Posts: 12734 Loc: fortfrances.on.ca	I really have to wonder why you would need to have DHCP assign a different but yet somewhat random IP. If you release the IP and then hard code another machine to temporarily use that IP, when you then try to renew tha lease, DHCP will flag it as BAD and take another IP from the pool. The network group probably would not like you doing this though. _________________________ Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
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#104659 - 2003-09-16 02:04 AM Re: Off topic: Force DHCP Server to assign new IP to client?
Allen Allen KiX Supporter Registered: 2003-04-19 Posts: 4562 Loc: USA	Thanks for the link to SMAC. It looks like a neat tool, and may just work... but man this scares me... quote: Warning: This tool may have the ability to cause crippling performance or other damage to the hosts and networks they run against. Because of this, some Antivirus software may identify this package as being a Denial of Service (DoS) agent. Les, you are right, why bother changing an address to another seemingly random address.... well had I not been part of this I would have asked the same thing. Basically, the address assigned to the pc is something like 10.10.20.0 with a submask of 255.255.248.0. This is a usable IP, but our corp offices have something against it when monitoring use through the firewall.
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#104660 - 2003-09-16 02:10 AM Re: Off topic: Force DHCP Server to assign new IP to client?
Les Les KiX Master Registered: 2001-06-11 Posts: 12734 Loc: fortfrances.on.ca	Hmmm... if the corp network guys don't like it, they should exclude it from the DHCP pool. I presume they are in charge of the DHCP and therefor the pool. So what part of it do they not like... the part of it ending with 0 or the mask? Try my trick to force the DHCP server to flag that IP as bad. _________________________ Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
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#104661 - 2003-09-16 02:18 AM Re: Off topic: Force DHCP Server to assign new IP to client?
Allen Allen KiX Supporter Registered: 2003-04-19 Posts: 4562 Loc: USA	In a big company, the left hand doesn't know what the right hand is doing... Basically, the folks who set up the DHCP server are not talking to the folks controlling the firewall. I think I will give your suggestion a shot tomorrow... Thanks guys, I let you know.
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