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I don't know if it belongs on serverfault or stackoverflow so you can move it if nessecary.

I am wondering if it's possible to reserve a group of IP addresses from DHCP without providing MAC Addresses to DHCP? Windows RAS does that so in DHCP Console you can see entry like Reserved for RAS for 10 or so addresses that have no MAC Address. I would like to achieve similar thing for the device that acts as DHCP Relay. I have to help to make the device send some kind of flag or empty mac address to DHCP to reserve the addresses?

For example:

enter image description here

share|improve this question
What kind of DHCP server? – Shane Madden Apr 25 '12 at 17:03
Don't add them to your DHCP-pool? – Bart De Vos Apr 25 '12 at 17:03
It's a special device that is getting developed. It basically has to ask any DHCP on any network to reserve IP Addresses (like 10 of them) for any upcoming devices that are connected to that special device. So it has to be for all possible DHCP servers out there. So I was thinking if Windows RAS can do it it's probably some flag or some frame that is sent to DHCP that makes the reservation with the comment. – MadBoy Apr 25 '12 at 17:05
Basically the device needs to reserve ip addresses before any device is connected to that device so no MAC or hostname is available. – MadBoy Apr 25 '12 at 17:06
something doesn't quite seem right about this special device, somehow I don't think I'd want it on my network if it had these strange requirements. – tony roth Apr 25 '12 at 20:59
up vote 4 down vote accepted

Windows RAS interacts with the DHCP server through management means (probably MSRPC) in order to reserve addresses - what it does will never work with a DHCP server other than a Microsoft one.

Nothing in the DHCP standard provides a means to tell a server, "I was one address for me, and a dozen for some friends" - heck, you can't even get two addresses on the same adapter. It's not a complex protocol.

Probably the best you're going to do is to have this mystery device send a bunch of fake DHCP client requests sourced from different fake MAC addresses, to stake out a bunch of addresses.

share|improve this answer
+1 for the last sentence, that's basically what I was going to say – Mark Henderson Apr 26 '12 at 1:25
Thanks. It's mobile board that is supposed to be communication device between router's some other devices. I don't know much about it just that it works that way as I described. Probably nothing fancy about it just that it wants to reserve IP Addresses for those mobile devices. – MadBoy Apr 26 '12 at 7:00

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