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10.4: A fix for Internet Sharing not issuing IP addresses Network
Tiger only hintI 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 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 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.
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10.4: A fix for Internet Sharing not issuing IP addresses | 4 comments | Create New Account
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10.4: A fix for Internet Sharing not issuing IP addresses
Authored by: ALinecker on Dec 15, '05 10:56:07AM

Turn on Websharing and see what happens. Internet Sharing has had a bug since 10.2 where you need to open port 80. Enabling Websharing does just that.

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10.4: A fix for Internet Sharing not issuing IP addresses
Authored by: DiMaestro on Dec 15, '05 08:55:16PM

That's because DHCP uses UDP. Enable UDP and DHCP will work, which will allow Internet Sharing to work.

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10.4: A fix for Internet Sharing not issuing IP addresses
Authored by: jonasyorg on Dec 17, '05 05:18:54PM

"stealth" mode means that when someone tries to connect to a closed TCP port, it will not send a reply with the RST flag set, it just doesn't reply at all.

if you would have looked closer you would see that dhcp stuff run on UDP, ergo it is the not accepting UDP which is the more likely cause.

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How to reset DHCP leases...
Authored by: xSmurf on Dec 18, '05 09:02:53AM
Kind of in the same line so I figured I'd post it here. It was useful for me, hope it will be for you. I have a server machine on a direct gigabyte link with the workstation. I recently moved that machine from OS X to NetBSD (Of course I run NetBSD ;). The problem is that OS X (on the workstation, which acts as the dhcp server for the direct link) would not reassign the proper ip, the one the server always had. This was a real pain in the rear since all my bookmarks we're set to use that ip. So if you wanna edit/remove the dhcp lease head to /private/var/db/dhcpd_leases and edit/remove the appropriate entry. Restart internet sharing and tada :D This works really well if you have only one machine on the other end.

SnitchCTL :

PM G4 DP 800 / 1.25gb / 120Gb+80Gb / CD/DVD±RW/RAM/DL
- The only APP Smurf

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