RE: Preventing DHCP from allocating IPs

["Jimmy Sansi" <jsansi () ritzfoodservice com>]

Not being able to distinguish between a valid client or
not from a network perspective makes it pretty hard. You can
easily stop this accross the board (with a router, etc).

It may be a bit more of a hassle but if you know the valid
clients MAC address ahead of time you could filter out that
way as well. However its not foolproof against a malicious
person intent on gaining access.

In regards to wireless, outside from the above I have seen
implementations that use a VPN connection that must be
established before you can access any network resources.

-Jimmy

-----Original Message-----
From: Sarbjit Singh Gill [mailto:ssgill () gilltechnologies com]
Sent: Monday, December 02, 2002 10:46 AM
To: security-basics () securityfocus com
Subject: Preventing DHCP from allocating IPs


Greetings all,

How do i prevent a client from getting an IP from my DHCP in an Ethernet
network. I know i could reserve IPs for all other clients and nobody gets an
IP unless reserved earlier, but i have hundreds of clients. I frequently
have visitors who need to plug in their laptops into the network and i have
visitors who are not allowed to plug in their laptops into the network and
get IPs. I do not want these visitors who are not allowed to access the
network to get an IP and start accessing internet through my network.

What about in a wireless environment. How do i prevent it in a similar
capacity.

Kind Regards
Gill