How do you keep users from stealing other user's ip??

[Chad Leigh -- Shire.Net LLC]

On Mar 23, 2006, at 11:25 PM, Mark Jayson Alvarez wrote:

> Good day,
>
>
>   We are trying to reorganize our local area network and I need  
> some tips on how you are managing your own lan...
>
>   We have a vanilla pc router with interface facing our private lan  
> and interface facing the Internet.
>
>  One problem which we are experiencing right now is that any user  
> from private lan can use any ip address he wants. If he boots his  
> computer with a stolen ip address, the poor owner of that machine 
> (not active at the moment) will give automatically up his ip  
> address to this user. The same scenario for public ip addresses.  
> Basically, we need to track down the users through their ip  
> address.. But this is trivial as of now since anyone can use any ip  
> he wants. Even if there is a solution out there to tie up his mac  
> address to his ip address..(sort of checking the mac first before  
> giving him an ip, possibly through dhcp..) still, users can just  
> download applications which will enable him to change his mac  
> address....
>
>  Now, where thinking about authenticating users before he is  
> allowed to use a particular network service(internet proxy, mail  
> etc.) because I guess it is a clever way of keeping the bad users  
> from doing something bad within your network when after all, the  
> reason why he is plugging his lancard to the network is to use a  
> particular service. However, it still doesn't keep them from  
> playing around and steal other ip addresses or mac addresses and  
> thus denying network access to those legitimate owners. I'm  
> thinking about tying dhcp with authentication, and freeradius comes  
> to mind.. I just need some more tips from you. User's workstations  
> are mixed Windows and *nixes. Some have laptops with wireless  
> interfaces.
>
>   Any idea how to handle this situations??

Why do you have bad users?  (I assume this is some sort of company?)   
Set a policy and punish those that screw around.  Most companies I  
have seen do not give admin privileges to the users so the user  
cannot change his IP or MAC address and if you force them to use DHCP  
you can also tie the MAC to the IP.

This is not a technical problem per se but an administrative policy  
problem.

Chad

---
Chad Leigh -- Shire.Net LLC
Your Web App and Email hosting provider
chad at shire.net