RE: Firewall and DMZ topology

["Des Ward" <des.ward () ntlworld com>]

The first one does not have to use two separate firewalls, just have an
extra NIC to segment the LAN and DMZ.

You bottom two examples are as follows:

The first one is far too complex and was how I thought a DMZ was supposed to
be until I realised that it just wasn't needed.

The second means that all traffic has to traverse your LAN to get to the
'Unprotected' DMZ systems and also could leave your internal LAN open to
attack.

The main thing to remember is that the DMZ is designed to be accessible to
the outside world.  You do want this segmented from the rest of the LAN in
the easiest way possible.

Just my .002667 cents worth (After converting from the BRITISH and not
ENGLISH pound)

-----Original Message-----
From: Chris Berry [mailto:compjma () hotmail com] 
Sent: 10 June 2003 01:53
To: security-basics () securityfocus com
Subject: Re: Firewall and DMZ topology

> From: Christopher Ingram <cmi () crystalsands net>
> So, the below setup is not decent for a corporate LAN. Ideally, the DMZ 
> should sit on a seperate connection to the Internet from the rest of the 
> network, using a different ISP and therefore, different IP block. This 
> provides the most isolation.

I'm afraid I don't see how that:

internet --> Firewall --> Lan

internet --> Firewall --> DMZ

would be any more secure than this:

internet --> Outer Firewall --> DMZ --> Inner Firewall --> LAN

or this:

internet -->  Firewall --> LAN
                             --> DMZ

which are the setups that I've seen.  Can you give some 
justification/explanation on why you think that would be better?

Chris Berry
compjma () hotmail com
Systems Administrator
JM Associates

"All I want is a few minutes alone with the source code for the universe and

a quick recompile."

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