Unfathomable Network trouble

[Qeveren]

Here's an interesting problem. We're using a cablemodem connection through Rogers@Home, with two IP addresses. The cablemodem is connected directly to a hub, which is connected to 1) a Mac (he bought his own IP), and 2) the gateway computer running Linux, that shares the other IP connection with the rest of the computers in the house.

This setup USED to work fine, until there was some extended downtime here in Toronto. Now, while everyone can DOWNLOAD normally, anyone on the network behind the gateway cannot UPLOAD more than 10kb, before the connection stalls completely. The really, really strange part is, this problem disappears if the hub that shares the connection between the gateway and the single Mac is removed.

We've since replaced the hub, and all the cabling, to no effect. Any ideas, anyone?

Here's some pictures to help:

This doesn't work (but it should): http://members.home.net/qeveren/images/not_working.gif

This does work: http://members.home.net/qeveren/images/working.gif

Any help would be appreciated! Thanks!

-Colby

[EYoung]

You dont say if you tried connecting the CM directly to the MAC. Try getting that to work. Maybe Rogers lost the IP to the MAC?
Maybe the re-wiring abd cable shuffling caused the CM to lose the mac address of your MAC? Powering up devices in the right order can fix that. The mac address is the hardware address of the Apple MAC's network adapter, which some cable modems store.

[Qeveren]

Actually, the problem is more freakish than that. The Mac with his own IP NEVER has the problem. Only the gateway linux machine and the stuff behind it.

[EYoung]

After midnight my logic gets pretty weird, so here goes. Your diagrams indicate you are an experienced intelligent person, so I assume you have done all the usual debugging stuff already (based on what you know is possible). So take a long shot and debug the impossible. It's impossible for both Mac and Linux to download ok without two IPs from Roger's right? Maybe not. If by some miracle both boxes conflict on the same IP, then a speed buffering problem at the hub (say the MAC at 100 and the Linux at 10) on the upload could cause a lockup. (Speed lock cant happen on download). So I figure isolate each and prove the two dynamic IPs and mac's are correct. Start with the Mac only because it's the easiest to tinker. If the Mac's going too fast, someone at Roger's tech support can tell you how to slow it down to 10.
On second thought, try replacing the hub with a switch.
-- Eric

[Qeveren]

I'd thought of replacing the hub with a switch, or maybe going out for a router, but we don't want to spend any more money. http://www.speedguide.net/ubb/smile.gif

None of our machines are using dynamic IPs, however; they're all static IPs and properly configured (afaik).

The nice folks at Terayon (who make our modem) suggest it might be an electrical problem, either with the ground, or something wrong with the hub (which we've since replaced) or the cablemodem itself. *sigh*

I will win in the end. http://www.speedguide.net/ubb/smile.gif

-Colby

[Storm90]

You know sounds more like your seconed Ip you perchased is not release for your service anymore. I had this happen before. This is what I came up with. So in turn I had the provider release it again for me. Had to convince him . But in the end he did. All was fine after that. Just a thought! But might be worth the try! GoodLuck!