Firewall and DMZ topology

From: William J. Burgos (
Date: 06/07/03

  • Next message: David J. Jackson: "RE: Monitoring Tools"
    Date: 07 Jun 2003 23:06:03 +0900

    Greetings list,

    I would like to set up a SOHO network with a firewall and DMZ for mostly
    web serving and email. Of course, there are private PCs on the internal
    network, Windows and Linux.

    My connection is a dynamic IP on a pppoe and I already have an old
    laptop used as a simple firewall setup.

    I am considering separating my web and email server to a dedicated
    machine and placing it in a DMZ.

    In searching on the web, I came up with a few topologies and I would
    like to ask the list of their opinion.

    I have sketched out a few scenarios below:

    1. | Internet |-->| Firewall |-->| DMZ |-->| internal network |

    This scenario (1) puts the DMZ between the firewall and internal
    network. I have read that this is insecure as if the DMZ is compromised,
    so will be the internal network. Is this true?

    2. | Internet |-->| Firewall |--->| internal network |
                      | |--->| DMZ |

    This scenario (2) uses three NIC's for the firewall. One for the
    internal network, one for the DMZ and one for the Internet. I have read
    that this is a Three-legged firewall setup. The drawback is that I would
    need three NIC's for the firewall which is now a laptop with only two.

    3. | Internet |-->| DMZ with Firewall |-->| internal network |

    This scenario (3) places the DMZ with the firewall on one box and then
    to the internal network. My concern is if I can secure the DMZ from the
    firewall on one box. Is there a way to secure this setup?

    4. | Internet |-->| DMZ |-->| Firewall |-->| internal network |

    This scenario (4) places the DMZ before the Firewall which leaves it
    open to the Internet. Is there a way to secure this setup?

    I am trying to avoid having to get another box with three NIC's for
    Scenario 2, if possible. However, I would feel safer in a less easy to
    break in setup.

    Any comments or suggestions would be appreciated.

    Thanks in advance.

    William Burgos

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  • Next message: David J. Jackson: "RE: Monitoring Tools"

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