I have two machines, one connected to the net via DSL, the second connected to first via FireWire. The question is how to get Internet access on the second machine? Apple claims it's possible, but does not provide any setup instructions. So here's a solution that worked for me.
Tiger. Connected to Verizon DSL modem. Ethernet is first item in Network prefs, FireWire is second.
Ethernet port: DHCP with manual address. IP set to something in router range, that is, given router IP of 192.168.1.1, set the IP address to 192.168.1.x, where x is anything between 2 and 255.
FireWire port: DHCP with manual address, and IP address to a different network. For example 192.168.2.1 (the last digit must be 1). Now enable Personal File Sharing and Internet Sharing. In Safari, connect to your router i.e. http://192.168.1.1. You will see your DSL modem setup screen. Note your primary and secondary DNS IP numbers. That should be somewhere on the Status page or something similar.
Not connected to modem. FireWire is the only network port in Network prefs. Set it to DHCP. Apply. Note IP router number that machine B will select automatically. If different than IP FireWire port address on machine A, go to machine A and set its FireWire IP to router IP on machine B.
Enter primary and secondary DNS IPs that you obtained from your modem above in "DNS Servers" field, one per line. Enable Personal File sharing.
Both machines will have access to internet and be able to mount each other for file sharing. It is possible to have a FireWire camera or disk connected at the same time to the other FireWire port, and everything works fine -- but slowly.
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