Networking question!

[wkd9394]

Okay, here's my situation.

SMC 4-Port Router (Barricade SMC7004ABR)
Laptop NIC = Xircom 10/100 Network Card (XE2000) - replaced the original LinkSys NIC
Generic NICs on desktops
Rogers Internet Cable Modem (Toronto)
All computers are running Win98
All computer TCP/IP settings were config'ed as instructed by router manual
#1 Two desktop computers beside Cable Modem (in basement) - One is C850MHZ, other is P200MMX
#2 One desktop upstairs (3rd floor) - P200MMX
#3 One laptop upstairs (3rd floor, different room) - K6-350MHZ

All three desktops work when connected through router
No signal on laptop network card (therefore, no connection to router/internet) DOES NOT WORK
Moved laptop to #2 connection and DOES NOT WORK
Moved laptop into #1 connections and WORKS
Laptop also connects direct to cable modem and WORKS
Ethernet cables in basement are short (30metres) - I checked and they are not crosspatch; ie. R-L on both ends: Brown,Green,Blue,Orange
Tried setting the laptop network card to 10Mbits and HalfDuplex but DOES NOT WORK

Borrowed my friend's ThinkPad (P3-650MHZ) and tried the different connections.
DOES NOT WORK in either upstairs connections (#2 or #3).
WORKS in basement connection (#1)
Switched cable connection ports (ie. moved #3 connection to 3rd port on router) and DOES NOT WORK
Essentially, my friend's ThinkPad follows the same connection pattern as the original laptop
Moved upstairs desktop computer (#2) into laptop's original (#3) connection and WORKS

So, because the desktop works in all of the cables, does that mean either :

1) There is nothing wrong with the cables
2) There is enough interference with the longer cable lines that (2 different types of) Laptop NICs cannot pick up the signal, but a desktop NIC can pick it up.

I guess the next step would be to buy new (long) cable and test out the laptops again?!

Any suggestions?

On a side note, the network used to be hooked up through a Linux box acting as a server/router and a hub connected all the computers. This config work for 2 years, but up until a last month the laptop stopped working (hence the above changes).

 

[bbarnes]

The cables are all working properly it sounds like, and at least one computer works on each connection, so I would assume there is nothing wrong with the cables.

But I have never heard anything about laptop NICs not being able to pick up a signal (if the signal weakened)...

 

[ScottMac]

There's an 80-90% chance that you have a cable problem.

ESPECIALLY if you pulled & terminated them yourself.

I'd vote for checking the cables.

BTW: Big difference between "working" and "Working Properly"


FWIW

Scott

 

[spidey07]

my guess is cabling. carefully post the 8 wires on both sides of each problem connections. I'm guessing split pair (pins 1,2 aren't on same pair or pins 3,6 aren't on the same pair) or polairity mismatch (pin 1,2 is wired 2,1 on other end)



<< R-L on both ends: Brown,Green,Blue,Orange >>

- that is the indication of bad cabling.
should be reading pin 1-8 looking at flat side of connector pointing away from you:
W/OR
OR
W/GR
BL
W/BL
GR
W/BR
BR

the important part is pins 1,2,3,6 or the orange and green pairs.

 

[wkd9394]

The "ie. R-L on both ends: Brown,Green,Blue,Orange" phrase was just an example, not the actual configuration.

If the cables were actually at fault (mind you I'm a networking novice), how do you explain that the desktop would work with the connection, but not the laptop (two of them) ?! Someone told me that my problem may be due to an electrical signal problem with the SMC router. It can't "push" the signal far enough so the laptop NICs can work. However, the desktop NICs can read that weaker signal. This theory pretty much fits the problem...

 

[spidey07]

If your cabling is not up to spec or wired properly all sorts of strange things happen.

Some nics are better equipped to detect a polarity problem and adjust accordingly which could explain the desktop. correct category5 cable is good upto 100 meters and doesn't matter what gear is used.

so the question remains - on the problem connections how are they pined out and what kind of cable was used.

 

[wkd9394]

Actually, I got it working tonight! I plugged a 10BaseT 4 port Hub (generic I think) into the cat5 cable that connects to the router. Then I connected the laptop NIC to the hub. I guess the signal really was too weak for the laptop NIC to pick up, until the hub "boosted" the signal.

KRAP! Just got off the phone w/ my gf and she said it doesn't work anymore!!! She said the hub's and router's LED were flashing crazy! Donno, gotta check it out tomorrow night.

 

[Rhi]

Hahaha.

I'd bet money your wiring is hosed.

-Rhi

 

[spidey07]

REALLY sounds like a cable problem now.

 

[usmc666]

One more voted for hosed cabling. Like Spidey stated...bad cabling will cause ALL sorts of weird problems.

 

[Tallgeese]

<< I guess the signal really was too weak for the laptop NIC to pick up, until the hub "boosted" the signal. >>

FYI: Any halfway-decent router and hub would both "boost" (actually called "repeat") a data signal equally.

Everyone: Network stability is all about CABLING.
What works smashingly at 10Mbps can do all sorts of crazy stuff at 100Mbps.
You wouldn't believe how many problem networks I've seen where someone told the client to lay out big $$$ (relatively speaking) for new servers, desktops, etc., and yet serious Physical layer errors kept dropping the network time and time again.

With the flashing lights, sounds to me like a packet storm. A Physical layer error definitely. Maybe a rule or length being violated?

 

[wkd9394]

I purchased a Belkin 50foot CAT5e cable to test the network out. It works! I'm gonna purchase a longer CAT5e (75-100feet) and try that out. I guess it is/was a cabling problem...thanks for everyone's help!

BTW, for some reason, the laptop now has a grey horizontal line across the screen now! It's visible in all screens...argh, I guess the LCD is messed?!

 

[spidey07]

<< I guess the LCD is messed >>


I've seen poor homemade cabling do that before. Hope the network cable didn't permanently damage the laptop.































j/k glad you fixed it.

 

[ScottMac]

Ground loop?

Does it still have the bar when operating on the battery and/or with with network cable dicsconnected?

Good Luck

Scott