News, info, and opinion by Mac users, for Mac users.

April 25, 2008

troubleshooting

Internet Sharing issues reveal subnet snare

Posted Apr. 25, ’08, 9:17 AM PT by Dan Moren
Category | Troubleshooting

Internet SharingSome days, all your technology works. I’m not quite sure, but I think that’s the first and third Thursday of every month. Or maybe that’s street sweeping. Other days, the time you spent in the trenches of the IT industry come back to you in lurid detail: the smell of sweat, of fear, the screams pummeling your ears. Today was such a day.

The proposition seemed simple: I was connected to a wireless network at my local cafe, and I wanted to share that connection (over Ethernet or FireWire) with a friend of mine on his own MacBook. Easy peasy, right? Turn on Internet Sharing and connect a cable.

Well, that’s what I thought. Only it didn’t work. As Homer once wrote, “FAIL.” Very puzzling. His computer would get an IP in the 192.168.x.x range, and it even had Bonjour support—he could connect to my computer, we could chat via Bonjour, but he couldn’t get to the outside world at all. What. The. Hell?

Days like this—dark days where even souls fail to see the light of the sun—Google is your best friend. I searched on likely keywords for a while, then decided to narrow my focus to Apple’s support boards, where I found this illuminating post, which contained the following tantalizing detail:

Basically, both ports on the Mac Pro were given the same subnet. This confused the Pro, as it didn’t know which port to forward TCP packets. It was stopping all packets from the Mac Mini.

Ah ha. Now we’re getting somewhere. Unfortunately, there was no link directly to the post where he found the solution, but knowing that subnets were an issue, it was simple enough to assign a manual IP address to my Ethernet connection (I chose something in the 10.0.x.x IP range, since my AirPort connection was already using the 192.168.x.x range), give him a manual IP address in the same range, and voilà: Internet. Case closed. Well, except for getting to shout “I am the king of the world!” That got me some odd looks.

Now, if only Apple would design Internet sharing to be smart enough to take care of this for me. That would make me the happiest panda of them all.


1 Comments

nw_mike Author Profile Page said:

Great tip! I couldn't agree more that Apple should make this a "it just works" feature.

April 25, 2008 9:55 AM

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