Friwalls and networking

From: Damien Hull <dhull@digitaloverload.net>
Date: Tue Jan 23 2007 - 12:36:11 AKST

At last Fridays meeting we were surrounded by firewalls. I think there
were four IPCop boxes. To properly configure, setup and understand
what's going on with a firewall you need some basic networking skills.

Here's a short list. I'm getting everything from wikipedia. If I miss
anything let me know.

BASIC NETWORKING 101

   1. Local aria network - http://en.wikipedia.org/wiki/Local_area_network
   2. IP Address - http://en.wikipedia.org/wiki/IP_Address
   3. Network Classes - http://en.wikipedia.org/wiki/Class_C_network
   4. Firewall - http://en.wikipedia.org/wiki/Firewall
   5. DMZ ( picture of 3 legged firewall ) -
      http://en.wikipedia.org/wiki/Demilitarized_zone_%28computing%29
   6. Ports - http://en.wikipedia.org/wiki/Network_ports

Some of the information may be difficult to read and understand. Some of
the information on wikipedia was not written for the average computer
user. I had a hard time reading some of it. Maybe someone can add to the
list or create a better one. One with easy to understand information.

FIREWALL BASICS

Make sure your interfaces are on different networks. Here's an example

   1. Green network ( internal network ) could be 192.168.1.1
         1. Network address = 192.168.1.0
         2. Broad cast address = 192.168.1.255
         3. Net mask = 255.255.255.0
         4. Network Class = C
   2. Orange network ( DMZ ) could be 192.168.2.1
         1. Network address = 192.168.2.0
         2. Broad cast address = 192.168.2.255
         3. Net mask = 255.255.255.0
         4. Network Class = C
   3. Red network ( Internet ) DHCP
         1. Should be different from other networks
               1. if Red is 192.168.1.x you should change the Green
                  network to something else

NOTE

    * Notice that the Green and Orange networks are not the same. They
      can't be.
    * 192.168.1.0 can't be used for anything. It's a network address.
    * Connecting the firewall to a workstation requires a switch/hub or
      a crossover cable

BASIC PORT NUMBERS

   1. Web Server = 80
   2. pop3 email = 110
   3. SMTP = 25

I hope this helps. I left out a few things but this should be enough to
point people in the right direction.
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Received on Tue Jan 23 12:36:43 2007

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