intermittent connection on one computer

[johnorford]

We are in the Philippines, with two computers, and the problem applies only to one of them.
We use a SmartBro dsl service, connected by antenna to a Planet WRT-415 router.
Both computers are fed by cable. I run XP SP1 - I took out SP2 as it seemed to make my computer run slowly. The other computer didn't suffer and has SP2. We had problems that seemed related to DNS and I put in the OpenDNS IPs on both computers. We have no problems with DNS now. I don't understand ICS, so we presumably don't have it.
My computer suffers poor Internet connection. It will go off line for a few seconds or minute or two or five, return and go off again. I counted 27 interruptions during a four minute track on last.fm one bad night. Sometimes it won't return at all unless I restart the computer - log-off doesn't do it. Once I had to reinstall the network connection and local area connection.
I thought - LAN card? We had one that failed in a month. However putting the cable into the on-board LAN card gave me no connection at all.
All wiring has been checked. Since my long wire (19m) had to be made by crimping the cable I added two short factory-made cables to each end so that the crimped connection could be fixed down.
Just to repeat that it's not a service problem, as our other computer doesn't suffer.

[Snurfen]

A belter of a problem here John!

Ok, I'd try and isolate the error,
First off, swap the cables in the router end of things - literaly swap the RJ45s at the router. Where is the fault now?
If at all possible, take the faulty pc and physicaly move it to the working pc. Connect the problem pc up in the location of the good one using the cable previously connected to the good one.
Does the problem persist or has it gone away?
If you haven't isolated the problem this way, then take the good one to the location of the problem pc and hook it up there.
Does the problem persist?

Basically, I'm suggesting you try a fault finding routine so you can see if the problem is pc related, cable related, or port on the router related.

By judicious fiddling, cable swapping, port on router switching and pc moving, you should be able to narrow down where the fault lies.

My money is on the cable being suspect - crimping off an RJ-45 can introduce problems even to the most experience cable maker. I'm not quite sure how that extended cable was made up, but definitely sounds a bit dodgy to me!

[johnorford]

Thank you Snurfen - it is indeed a belter. I note that the light on the LAN card winks when I am connected but stops winking without going out when the connection breaks. Does that tell you anything? The crimped plugs were troublesome, so I plugged them into female/female connector blocks fixed to the wall. The crimped cable can't move now. The interesting thing is that I can always restore the connection by re-starting. Now obviously I could have a cup of coffee or whistle a tune and it might come back in time - but the re-start has worked every time without fail.

I will swap the cables at the router but it's quite a feat to swap computers, which is why I'd like to reason a few things out if possible.

[Snurfen]

The winking bit shows network activity, the light staying on says "I've got something plugged in but it's currently idle". (More or less - LOL ).

Sounds like a good patch setup you have there, so we'll hang fire till you have the time (and patience) to do the swap/isolate tests to give you a better picture. A royal p.i.t.behind, I'll admit, but can save a heck of a lot of head scratching/tool throwing in the long run.

*EDIT* I really should reread before hitting post! I meant to say it would be well worth the effort of ensuring that each of the eight cables in the back of each wallbox is amaking a good snug clean mechanical fit.

[johnorford]

Thank you again. All cables seem properly connected. I've transferred my LAN to no. 3 on the router. Now don't think I don't believe your diagnosis but I'm a pita too - I always want to know why. When the connection goes, it can always be restored by re-starting. But very often it will come on for a few seconds and immediately go again. I use the BitTorrent graph to monitor what's going on. For the life of me I cannot see how this can be caused by a poor connection. Could it be a faulty LAN card? I have a spare somewhere. If it could be a connection, then . . . .

[Snurfen]

Yep, it's pretty much going to be signal related, which usually ends up as a physical weakness somewhere between the signal entering the house and hitting the pc.
As it is location specific (so far) it's leaning more to there being this physical fault than from the actual service provided by the ISP.

Give the NiC replacement a shot - it'll be time well spent, but before you do that, try re-installing the NiC drivers on the troublesome pc.

[johnorford]

Thank you Snurfen - no it's not the ISP, though they do give us a rather unstable signal; there's no problem on the other computer. I'll just have to dig it out - probably in the wee small hours when the other computer isn't being used.