[ale] HOWTO: -> packet filtering firewall configuration using ipfw

[Courtney Thomas]

Greetings !

I want to define the rules for using "ipfw".

I understand that the default is .........
    everything is blocked.

Setup:     a lan w/gateway to the net for all nodes

Goal:       to permit incoming packets only from activity
                  initiated by the internal [to the firewall] lan nodes

I'd appreciate hearing from anyone successfully deploying  something
like this.

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Immediate particular questions are:

1- What are the packet type distinctions between..................
    ip, tcp, icmp, udp

2-What would be an appropriate "source" ip address range

3-I assume an adequate "destination" ip address range would simply be
the node addresses

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I'd appreciate a URL describing, in some detail, all this.

Thanks again to all,

    Courtney