RE: [fw-wiz] Strange setup

From: Melson, Paul (PMelson_at_sequoianet.com)
Date: 02/26/04

  • Next message: Mark Tinberg: "Re: [fw-wiz] Strange setup" 
    To: "franco segna" <fsegna@web.de>, <firewall-wizards@honor.icsalabs.com>
Date: Thu, 26 Feb 2004 14:24:02 -0500

    Franco,

    Without seeing the rule sets on either system, it is impossible to say.

    Clearly this design misses the point of a 'DMZ' network. There's no
    reason that I can think of for the ISA server to be dual-homed. There's
    no reason that outbound proxy traffic, RAS/VPN traffic, or reverse proxy
    traffic can't pass through two sets of firewall rules, one between the
    outside and DMZ, and another between the DMZ and inside. If you're
    tasked with redesigning this network, that should be first on your to-do
    list.

    That said, a possible explanation is that the ISA server is a reverse
    proxy for servers on the internal network, and the firewall only allows
    inbound traffic to the DMZ for NAT purposes. In this situation, the ISA
    server could provide extra access controls at the application layer in
    the form of authentication or restricting access to specific
    pages/services through destination lists. Workstation browsing and
    other inside->out traffic could pass directly through the firewall
    without going through ISA.

    That's just a theory, though. Looking at the rules on both the
    SonicWall and the ISA Server will give you a better idea of the intended
    function of this design.

    PaulM

    PS - I can't help but notice that a disproportionately large number of
    European, and specifically German IP networks (including my previous
    employer's) have been designed using internal addressing schemes that do
    not conform to RFC1918. Anybody have an educated guess as to why this
    is? It's just a personal curiosity of mine.

    > -----Original Message-----
    > Hi everybody,
    > I'm being confronted with the following existing setup:
    >
    >
    > T1 --------------------------------
    > (Internet | LAN backbone |
    > and VPNs) ------------+---+---+-+-+-+-+---
    > | | | | | | | |
    > | +-------+ local x.x.x.254/24 | | | | | | +-
    > | | Sonic +---------------------+ | | | | +-
    > +--+ Wall | | | | |
    > | Pro +------+ | | | +- SQL
    > +-------+ dmz | | | +-- mail
    > (?) | +--------+ | +--- etc.
    > | | MS ISA | |
    > +--+ 2000 +------+
    > | Server | x.x.x.251/24
    > +--------+
    >
    > The public web server is hosted elsewhere. The LAN comprises
    > 30 workstations.
    > To complicate the matter, the LAN address family x.x.x. is
    > NOT RFC1918-compliant (and is conflicting with existing
    > Internet hosts).
    > The system is up and running, but I cannot understand the
    > bypassing of the ISA server through the direct connection
    > firewall/LAN. And the meaning of DMZ seems to be lost.
    > Anyone can help me to understand the matter ? Thanks in advance
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  • Next message: Mark Tinberg: "Re: [fw-wiz] Strange setup"

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