wireless bridging?

I don't have any wireless devices of my own, but a certain lady of my acquaintance has a Powerbook that she would sometimes like to use from the couch without dragging an ethernet cable over. Can my iMac behave as a wireless base station? I created a network on the iMac, and was able to see it from the laptop, but the laptop wasn't able to get to the interweb. Is there some extra trick I need to do to get the iMac to route between wireless and ethernet?

Update / Summary: "That should work", followed by "it would be a lot easier to just buy an Airport."

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38 Responses:

  1. justinjs says:

    Look in "Sharing" in the System Preferences, then in the "Internet" tab.

    • jwz says:

      Did that. I think the laptop isn't getting assigned an IP from the imac.

      • justinjs says:

        I assume that you've actually checked that it's the IP assignment that is not happening?

        (using either ifconfig or the system preferences network panel, depending on what kind of mood you're in...)

        Once in a while I've found the osx interaction between dhcp and the airport network selection to be weird, usually fixed by simply turning the airport off on the client machine, then back on via the menubar.

      • curious_au says:

        Just reading this and what you wrote here, when I do this ( sharing ethernet out over Airport, I don't create an ad-hoc wifi network first, which is what I think you're doing. I just go preferences->Sharing->Internet; from: Built-in Ethernet; to: AirPort. This creates a wifi network with a DHCP server that everyone can see.

        Good luck.

  2. fflewddur says:

    Did you enable "Personal Web Sharing" under the firewall settings?

    • jc says:

      Er, "Personal Web Sharing" refers to the built-in Apache web server, not Internet Connection Sharing.

      • fflewddur says:

        One would expect that, yes, but it's the only way my PowerBook can share an ethernet connection. If the Personal Web Sharing service is disabled, clients don't pick up an IP address.

        • duskwuff says:

          That's a red herring. Personal Web Sharing has nothing to do with Connection Sharing.

          • drbrain says:

            I have been unable to connect to the internet through Internet Sharing without the firewall disabled. I never looked to see exactly what I needed to allow through the firewall.

            Since Personal Web Sharing also allows port 80 through the firewall, this may be why it magically works.

  3. jpallan says:

    <lj user="crschmidt"> and I had this issue in the airport at SFO yesterday. His explanation was thus:

    I had a connection to T-Mobile's hotspot in the airport. He said that wasn't adequate to share the connection with him, because I was using the AirPort card to receive the signal, and could not receive and broadcast from the same card at the same time.

    He often shares connections with me, but these are connections he makes through Bluetooth (GPRS) and then shares over AirPort to my computer.

    Makes as much sense as anything else, eh?

    • vxo says:

      Indeed, I believe this is the case. I handled this once by sticking an old D-Link AP on the ethernet port and telling it to share from the Airport card to the ethernet port. Worked like a charm, though it's kind of inelegant as it requires extra hardware.

    • justinjs says:

      Not the same issue. Jamie asked about bridging between ethernet and wireless, which normally works just fine.

      That said, I don't know what the solution is -- this Just Works for me.

      • jpallan says:

        Well, and keep in mind that I'm an extreme layperson, I believe that Ethernet and wireless happen on the same card in a Mac. I may be totally wrong, but the "you can broadcast or receive but not both" theory would be explained by that, if it's true.

  4. dormando says:

    For bridging laptop -> laptop with the girl's powerbook, I got lazy and created another network profile on the macs. The "bridged" profile defined a local IP on each end, then enabled NAT + fiddled the firewall settings a bit. Took me about a minute and a half, and I didn't have to dick around with DHCP not working.

  5. lohphat says:

    Why spend this much time on this when there's a commoditized solution for $80 in a NAT+SPI+WPA wifi firewall from multiple vendors designed to specifically solve this problem for sharing IP connections?

    • otterley says:

      Seconded, with the exception that one can obtain such devices for well under $80 nowadays.

      • lohphat says:

        Well $49+$10 shipping may sound cheaper than $80 (now $70 @ Fry's), but it's a false economy when you get shipped a v.1 router when the current is v.3 and you spend another $40 in trying to return it (if you can at all).

        I shop @ Fry's expecting the fast-food/TSA reject not to be able to answer my simple questions because I know they'll take their stuff back no questions asked.

        Also, the average Joe doesn't understand that the wifi channel needs to be tweaked based upon the locale -- if you choose a channel already in use by your neighbor, you've already lost bandwidth. You have to survey the existing nets in use, then choose channel 1-6-11 to get full channel separation (all the other channels have cross-over, thus reduced capacity).

        I've deployed over 50 APs and it's not all hearts and flowers. I'm gravitating towards the newer netgear stuff as linksys has burned me with too many flakey units.

    • jwz says:

      You make a very good point.

      However, I thought that then I would hear "why did you spend $80 on that dingus when your new computer came with the same thing built in? Stop overthinking it!"

      • mark242 says:

        Remember, you're in the Mac world now. Our default answer to problems is to spend money and make the problem disappear.

      • adolf says:

        I'm sure that it will comfort you none that the most popular iteration of such a device is the Linksys WRT54G, which Wal-Mart sells for $60, and which runs Linux.

        It Works For Me(tm). But, then, so did the SB0100 that you managed to not procure...

        At least, $60 is less than the $80 that you seem to think that it should cost.

        • jwz says:

          For the record, I think that Linux is still a fine choice for things that don't have screens or other peripherals. Servers? Cool. Embedded? Cool. Desktop? Forget it.

          • Even within "desktop" linux can work - I'm using an old PC now for art, as a GIMP engine right next to my easel. It's great and the wacom tablet works fine. I'd never get the same performance running Windows on it (it's 600Mhz). As a bonus, I can grab images and stream music from the downstairs (windows) PC. Oh, and some things - like the start-up time of the wireless net connection - are a pleasure.

            I have to have a commercial OS on the main, general PC in the house, because Linux can't quite compete, but it's great for a lot of the rest.

            • jwz says:

              Yes, I understand that a number of people find Linux desktops trouble-free and easy to use.

              Good for them. Go forth and enjoy.

      • greenmustard says:

        I bought a Linksys WRT54G router after being frustrated with obscure problems using a slackware linux box for routing. I just wanted it to work. And for the most part, it does, but it seems everyone who buys consumer-level network stuff these days is whipped into accepting junk that has to be rebooted once a week. And they think that's okay.

        I guess my point is that switching to hardware won't necessarily make things better, just easier. When it fucks up it needs a reboot, and at worst a bios flash. Also, do NOT get a v2.2 WRT54G.

  6. causticjb says:

    The iMac can do sharing. Be sure you use OS 10.3.x or newer, DHCP doesn't properly fire up otherwise. Go to the Airport, turn on the card and create a new SSID. Next, go to the System Menu, and hit "Sharing." Share the Wireless card. It SHOULD just fire up and work. On the client side, make sure the client is associated with the iMac's connection.

    Under 10.2.x and previous versions, you'll have to manually start up dhcpd, and manually configure the dhcpd configuration file. There is a widget you can download to do it for you, but it's not freeware.

  7. danomite55 says:

    In the Internet pane of Sharing, "Share your connection from" should be ethernet, "To computers using" - "Airport". The only problem I've had is that I found that I had to manually enter a DNS server on the computer that is connecting to the new wireless network.

    • decibel45 says:

      In the interest of "It Just Works" (tm), I'd recommend an airport express. Not only do you get nice simple wireless, but you get to play music from iTunes on the audio device of choice from it via the wireless connection.

      • edouardp says:

        Yes, I have to admit that once you starting snorting that Apple-based goodness, it gets very hard to stop. I've got two Airport Expresses at home (but in my defense I won one of them when I picked up Tiger a couple of months ago). One is set up to bridge my ethernet to 802.11g, and the free one is hooked up to my sound system so iTunes can stream music to it. I used to do it the Linux/SPDIF/CMI8738 thing with a 10 meter RF cable strung under my house between rooms, but now that's just a distant, non-Apple, memory.

  8. cwilllu says:

    You do like to torture yourself, don't you :p

    Buy the damn home firewall/switch/access point.

    My experience:

    I've got an DI-784 (a/b/g, I also had a straight b/g), been working for months with no mysterious issues. 'A' is probably ideal if you don't mind the extra cost, don't need too much range, but it's a pain if you already have b/g built in to the laptop. This is with dhcp disabled (handled by another dlink I already had, which also provides nat to the web.)

    The Linksys 54wrt's (b/g) have been good to me as well, except for a minor ipsec issue that prevented multiple outgoing vpn connections at the same time (the d-links don't have this problem and hence they are what we're recommending to our users; otherwise the linksys is a clear winner). Don't bother with the open firmware junk if you can help it. I'm running one of these in an production environment, providing dhcp/firewall/switching for a small 8 ip dmz, going into a couple openvpn servers and a test bench machine, also providing an outgoing vpn for those times when you really can't go through a proxy. Again, flawless.

    Seriously, the 80$ box is the simplest way to make this work; the only way I would consider doing anything more is if I seriously needed to secure the wireless portion... in which case I would still use the box, but piped through a vpn and out to the network from there.

    I can't imagine a sane network config that you couldn't get this working in under 10 minutes. Just don't let wep get to you.

    • jesus_x says:

      I swear to god WEP hates me. I pride myself on being able to either fix any problem, or find a solution to it, but every time I set up wifi for a client, I have to do the wep key stuff at least thrice. And it's not just typing it in wrong, as I'll check, I've typed it in flawlessly, or I run around with a sneakernet floppy, and I still have to do it half a dozen times. I hate WEP and it hates me.

  9. lohphat says:

    The issue is why utilize your PC's processing and CPU bandwidth when it can be off-loaded to a box that can handle n nodes as well as the one off. In addition these "internet sharing solutions" after inject a fragile dependency of components (DHCP, reverse DNS, blah blah blah) that make it ugly and buggy.

    Could it do the job? Yes.

    Should it do the job? No.

    That's why there are dedicated sound and graphics hardware -- to off-load the CPU instead of it doing it all.

    Using a PC as a router falls into the same camp. It's a poor application of available resources. There's a reason routers and f/ws live in their own box and the market supports it -- because that's where they belong architecturally, not at the nodes.

  10. drjohn says:

    According to Think Secret, this may be addressed in the next update: "...the latest build corrects an issue with AirPort and Internet Sharing..."

    The update is imminent, perhaps this week, according to other sources the rumor mill. Hope you get it working.

  11. suppafly says:

    I love how the solution from all the mac experts is to just buy a $80 wap. Of course mac's just work if you buy a lot of extra dedicated hardware, but why would you need to do that just to share an internet connection between 2 laptops..