Welcome to the MacNN Forums.

mfox · Nov 24, 2002, 06:45 PM

My AirPort-equipped iMac is running OS 9.2.2 and is talking to a Cube running Jaguar and set up as a Software Basestation. The Cube is connected to internet through a Sympatico high-speed connection. The internet connection of the remote iMac works well in most cases, but I find that I am consistently unable to connect to certain websites (Sympatico, Bell or Future Shop). I am also unable to use the Software Update control panel on the iMac; the connection is attempted but never made. I'm wondering if this has to do with some blockage of these sites against a non-direct connection. Can anyone explain this to me or suggest a setting that will make the remote computer work in these situations?

ghporter · Nov 24, 2002, 07:02 PM

By "remote" I take it you're referring to the computer that's not directly connected to your Internet connection. I think you're running into a local firewall or proxy problem. In other words, something (probably something acting like a firewall) is blocking either your requests or the replies.

Take a look at everything running on your client computer (that's the wireless one), and compare that to the one that's directly connected to the Internet. Either the Software Base Station or the client's AirPort set up is probably to blame.

mfox · Nov 24, 2002, 07:30 PM

Thanks for your reply, Glenn. The AirPort on the client running OS 9 is version 2.0.4, whereas the host is running AP version 2.1 on Jaguar. The firewall in the Sharing panel of the host has been left off. I don't think there is a firewall setting on the version the client is running. What should I look for?

ghporter · Nov 25, 2002, 10:55 AM

Did you see if the OS X firewall (in the Sharing pane under System Preferences) might be enabled? I think it's on automaticaly. Since you're running the Software Base Station, I think the OS considers that "sharing," so it could be a factor.

This is one of the reasons I'm willing to spend the extra money and buy a hardware base station-too many interconnected software issues!

Camelot · Nov 25, 2002, 10:46 PM

Does your ISP use PPPoE to assign an IP address to your Jaguar machine?

If so, your problem is probably the MTU (Maximum Transmission Unit) on your iMac.

By default, your iMac's AirPort card will be configured to use the ethernet default MTU of 1500 bytes, which basically means that it 'talks' in packets of 1500 bytes.

When using PPPoE, there's an overhead of 8 bytes per packet (if I remember correctly), so your Cube will be using 1492 on the line to your ISP. Therefore the 1500 bytes from your iMac won't fit.

The solution is to lower the MTU on your iMac to be 1492 or less.

The only way I know of changing the MTU under Mac OS 9.x is to use the tool IPNetTuner. It's a $30 program, but comes with a 21-day trial so you can see if it works before you pay.

mfox · Nov 26, 2002, 07:51 AM

By default, your iMac's AirPort card will be configured to use the ethernet default MTU of 1500 bytes, which basically means that it 'talks' in packets of 1500 bytes.

When using PPPoE, there's an overhead of 8 bytes per packet (if I remember correctly), so your Cube will be using 1492 on the line to your ISP. Therefore the 1500 bytes from your iMac won't fit.

The solution is to lower the MTU on your iMac to be 1492 or less.

The only way I know of changing the MTU under Mac OS 9.x is to use the tool IPNetTuner
_____________________

Thanks for that, Camelot; I didn't know anything about the bytes per packet, and I never encountered a setting for this in either OS 9 or X. I will try IPNetTuner, but I'm also wondering from your answer whether there is a way to set the MTU in OS X without any external program? I have OS X.1.5 on the client as well as 9.2.2; I just haven't been running it.