iptables and dhcp configuration

[Tim]

On Wed, 2012-08-08 at 15:26 +0530, Jatin K wrote:
> is there any way or method available to configure iptables to allow only 
> dhcp server assigned ip , means if user manually sets his/her systems ip 
> address then Linux gateway(FC16) should reject it .
> user must use the ip address which is assigned by dhcp, ( dhcp server is 
> running on the same machine where iptables are installed, and machine is 
> acting as a gateway )

You could script something so that a computer added to the DHCP pool
gets added to the iptables rules, but can you actually achieve what you
want?

Are you simply blocking the client's access to the DHCP server (gateway
on it)?  That's easy enough to block via an IP rule.

Are you trying to block the client to anything, in which case your
gateway must actually be *between* the client and other things (merely
being on the same network isn't enough).  Otherwise, the gateway can
simply be bypassed.

And if a user manually assigns themselves the same IP, coincidentally,
should it be allowed or blocked?  Do you just care about the address, or
do you need a DHCP client acknowledge?

It sounds more like you need some sort of authentication system, rather
than just IP assignment.

-- 
[tim at localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored.  I
read messages from the public lists.