Dec 15, '05 06:28:00AM • Contributed by: stottm
I found a problem with Tiger not working with Internet Sharing to both a PowerBook and a Dell laptop. It was a brand new PowerMac G5 with dual Ethernet. The PowerMac G5 obtained an IP address from the internet provider, and would set its internet-shared Ethernet port address to 192.168.2.1. The problem was that the laptops did not receive an IP address, and kept failing over to the automatic IP address of 169.x.x.x.
It turns out that Tiger introduced a GUI firewall feature under the Advanced button on the firewall, and in my zeal to secure the PowerMac G5, I turned on Stealth Mode and Block UDP packets. Internet Sharing only worked once I turned these two options off. Then instantly, everything worked as it should.
It may be possible to configure the firewall and NAT features outside of the GUI, using the Terminal.app and some Unix black magic in the configuration files, so that the stealth mode and UDP blocking only occurs on the external ethernet interface, and not the internal one. However, it seems that the GUI applies these settings to both. I am not sure if the required Personal Web Sharing allows the Apache web server to be exposed to the external interface which would place it in the wild -- and that is something I really don't want to do. I will be recommending an external Linksys router to avoid having to worry about hack attempts. That would negate the entire need for Internet Sharing.
I suspect the problem really rests on Stealth mode, as dhcpd won't be seen and won't respond. This will most likely affect all internet sharing -- i.e. Ethernet, AirPort, FireWire, etc. I unfortunately didn't have time to fully test this out to see exactly what was going on, but I hope this information is useful to someone ... and that those in the know will respond in the discussion.
