IP address conflicts

Ted Mittelstaedt tedm at toybox.placo.com
Tue Sep 28 10:19:29 PDT 2004

> -----Original Message-----
> From: Eric Crist [mailto:ecrist at secure-computing.net]
> Sent: Tuesday, September 28, 2004 6:38 AM
> To: Ted Mittelstaedt
> Cc: russell; bsdfsse; freebsd-questions at FreeBSD.ORG
> Subject: Re: IP address conflicts
> Hash: SHA1
> For what it's worth, aside from some reconfiguration that could be a
> little time consuming, I would suggest putting the servers on a
> different subnet that everything else.  If all the computers that are
> not servers are supposed to be configured for DHCP, insert a FreeBSD
> box that filters out any addresses outside that subnet.
> i.e. Server IP addresses are all thru  Set
> your DHCP server to only assign IP addresses above and up
> or so.  I'm too lazy to do the math right now, but use the appropriate
> subnet mask and filter all the other stuff out.  Aside from those
> students disrupting some of the other users on the network, they can't
> spoof the servers anymore.

No, they just spoof the IP address of the router that the servers are
behind, and accomplish exactly the same goal.

It actually makes it easier because instead of multiple servers and multiple
IP numbers the attackers need to spoof, they only now need spoof 1 IP
number -
that of the router the servers are behind.


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