DHCP Reservation questions

[andrew4728]

Hey all, just had a question about DHCP Reservations. My organization currently staticly sets each PC, which is proven to be a pain in the butt and also restricts us from using services such as PXE to boot PCs and install windows over network. I'd like to look into using DHCP, but my boss does not like the idea of allowing anyone to plug in a laptop or any other device and have access to internet and other resources on our network. I have never setup a DHCP server in windows, but would like to look into it.

Question :
Let's say I have 50 PCs on the network, and I setup 50 individual reservations for each PC and limit the DHCP scope to only those 50 addresses, would it assign any of those reserved IPs to a non-reserved PC if it plugged into the network?

for example, computer #1 is shutdown for some reason, leaving that reserved ip open. If someone brought a random laptop from home and plugged in, would DHCP assign the laptop computer #1's ip because it is available and no other ips are available in the DHCP Scope?

Also, if that is the case, would the following remedy that situation ? (if this is even possible in windows DHCP ):

Set scope 192.168.1.101 - 192.168.1.150 for all reserved addresses.
set scope 192.168.2.101 - 192.168.2.150 for all public DHCP clients

Then using ACLs, restrict what the 192.168.2.x network has access to.

Would that prevent any public PCs from automatically recieving a 192.168.1.x ip ?

(Yes I know anyone can manually set their IP info if they know the ip scheme, and DHCP Reservations are not considered a security measure)
I also do know that keeping a list of mac addresses for each pc would be a pain, but I feel it would be easier than staticly setting each PC with all IP/DNS settings

Side note : We do not have any managed switches, nor do we have any money for special programs (non profit).

Thank you for your assistance!

 

[elgrandeperro]

First, I am not a DHCP expert, but have admin-ed a few.

So a reservation is just that, if the device goes offline the reservation isn't opened up. A slimey user can take the reserved device offline (turn a printer off, for example) and then assign statically, of course.

I have read about "class id" in Microsoft DHCP that restricts DHCP by a predetermined class id. The users would have to use the "ipconfig /setclassid" commands to establish communication.

http://thelazyadmin.com/blogs/thelazyadmin/archive/2007/02/08/DHCP-User-Classes.aspx

 

[andrew4728]

Awesome. I didn't know that existed. Thanks a lot man.

I am going to read up on that. Seems like it could be quite handy for what I am trying to do.

Appreciate it.