Interesting network problem.

[Kevin D]

Ok, so what's in a switch that can fix a possibly damaged network port or wire?

Cable modem & router are in a living room closet. Wire runs through the attic to a back bedroom. Wire tests good with a basic tester. Connect wire from router direct to pc, pc gets ip address but internet is slow (usually never fully loading a page). Won't even load the router (but will pull up the login prompt).

Put a 10/100 switch next to computer, wire from in router, and wire out to pc. Internet works fine, fast as can be.

Put the same switch next to router, wire from router to switch, and the attic wire from switch to pc gets the same results as running it direct from router.

I'm content leaving a $30 switch in the back and assuming something is wrong with the wire, but I'm really curious why it will only work with one on the pc side of the wire???

Any thoughts? I'll probably eventually string a wire out to test with, but very strange.

Kevin D.

[Hdale85]

Wow that is strange......I'm sure you've tried different ports and what not. Maybe satan has possessed your router

[Kevin P]

Some switches/ports are more tolerant of marginal cables than others.

Also, sometimes a cable will work fine in a 10/100 setup but will fall flat on its face as soon as you plug it into a gigabit port.

Is this a cable going through the wall? Try re-terminating it and see if that helps. Most of the time ethernet cable problems are with the connectors, not the cable itself. Since you say the problem goes away when you put the switch on the PC end of the cable, try re-terminating that end.

[PewterTA]

Something in the cable isn't right I would think. I'm wondering if the cable is wired backwards, this would cause the problem you are getting. Meaning one end is wired up as 568-A method and the other is 568-B method. It basically creates a X-over cable.

With the switch plugged in, I'm betting it auto configs itself for either type of cable and that's why it works fine.

The only other things that could cause problem is the cable is not made for Giga-bit (like Keven-P said) and you're getting too much resistance...but I doubt your run is too long for that. Or there's a break in the cable somewhere and the powered switch outputs a higher signal.

[Kevin P]

If it were the X-over issue, the switch would have "fixed" it even when it was placed at the router end of the cable. Since the switch only "fixed" it when plugged in to the PC end, that leads me to believe the termination is faulty on that end of the cable. Also, his cable tester would have shown it if it was wired for X-over.

Sometimes the RJ45 doesn't seat properly in certain ports, or the teeth didn't pierce the insulation properly when the connector was crimped on, causing a weak signal path. That's why I suggest re-terminating the PC end of the cable.

When I built my file server a couple months ago, I plugged a known working (homemade) cable between it and my gigabit switch... and it wouldn't connect. It caused one of the lights on the switch to flash repeatedly, indicating some kind of trouble. I tried another cable (also homemade), and it worked fine.

[Kevin D]

Yeah I'll have to play around with it this weekend and see. Won't be hard to re-terminate the ends.

Kevin D.

[audioqueso]

Is this a real router or a home-type router (Linksys stuff, etc).

COULD be the wire, but it looks more like it's your pc NIC not being able to tolerant that run. Without knowing any specifics, it sounds like the router is set to GigE, but the pc NIC is only 100base. Put a switch in the middle, ports are on auto, switches GigE to 100... it works fine. But that's not the case... as soon as you put switch on the other side of the long run, it doesn't work. So it's not a layer 2 issue.

Did you make that cable? I would suggest to make another one, a short one. Now connect the pc directly to the router again. If it works, it could be the long run cable faulty, OR perhaps the cable may be too long for the pc NIC to handle. NIC could be faulty or something.

[impala454]

If the only difference between working and not working is that the long cable is between the switch and router vs the switch and PC, it's got to be a cable issue. My guess is it's terminated different on each end (probably as a crossover). Go reterminate both ends and make sure you use the same pattern (doesn't really matter as long as they're the same). It should just be a straight through cable.

[Gianluca]

Lenght?

Anything close to 100 meters or 300 foot?

Switch acts as a bridge in this case and retransmits signal.

But my quess is the terminations on the cable. It is minimum CAT5?

???

Gianluca

[Kevin D]

Maybe 30' maximum. Standard CAT5 crimp RJ45's. Too busy to try any suggestions yet.

Kevin D.

[littlesaint]

Sounds like it could be an auto-negotiation problem with the NIC in the PC. When the connection is slow, check what your NIC in the PC reports for its speed and duplex. If it shows half duplex, it's not able to properly negotiate over the cable distance. Sometimes it will get the speed right by sensing the voltage on the line, but duplex always defaults to half when negotiation fails. If you can set speed/duplex in the router, you could try forcing both ends to 100/Full and see if that helps.