This would require some effort to configure and maintain, but what about
using DHCP reservations?  This will accomplish the goal of only allowing
approved PC's on your network.

-Andrew

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Charlie Kaiser
Sent: Monday, May 16, 2005 9:40 AM
To: ActiveDir@mail.activedir.org
Subject: RE: [ActiveDir] Secure DHCP

At the lower layers of the OSI stack, the only way I'm aware of to block
computers from getting an IP address is to use port-based authentication if
your network hardware supports it. As Al mentioned, quarantine networks are
becoming a more realistic solution, but don't address the basics of DHCP.
Using IPSec to ensure only trusted computers can get access to resources is
a decent solution as well; the rogue PC can get an address, but cannot
connect to anything except perhaps the internet. Not simple to set up,
though...

Hmmm. Maybe we can develop a power over ethernet solution. Run 220V AC
through the ethernet cables and put a high-pass filter on the legit
machines. Then, if someone plugs a rogue laptop into the network, the laptop
gets a little hot... :-)

**********************
Charlie Kaiser
MCSE, CCNA
Systems Engineer
Essex Credit / Brickwalk
510 595 5083
**********************
 

> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Dan DeStefano
> Sent: Monday, May 16, 2005 7:00 AM
> To: ActiveDir@mail.activedir.org
> Subject: [ActiveDir] Secure DHCP
> 
> I am wondering if there is any way to secure DHCP from assigning 
> leases to PCs that are not authorized on the domain. I imagine that 
> this is not possible since, in order to authenticate, a PC needs an IP 
> address.
> 
> The problem is that the other day we had a rogue PC plug into our 
> network and, though probably coincidental, our browse list was messed 
> up afterwards. So I have been tasked with finding out if there is a 
> way to prevent unauthorized PCs from obtaining IP leases on our 
> network (other than disabling all jacks not in use, which is what we 
> will be doing). If not, does anyone have any suggestions on how to 
> prevent the above situation in the future?
> 
>  
> 
> _________________________
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>  
> 
> Daniel DeStefano
> 
> PC Support Specialist
> 
>  
> 
> IAG Research
> 
> 345 Park Avenue South, 12th Floor
> 
> New York, NY 10010
> 
> T. 212.871.5262
> 
> F. 212.871.5300
> 
>  
> 
> www.iagr.net <http://www.iagr.net/>
> 
> Measuring Ad Effectiveness on Television
> 
>  
> 
> The information contained in this communication is confidential, may 
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