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Question on NIC's speed and duplex

Posted on 2004-10-02
Medium Priority
Last Modified: 2013-11-09
I have set up 3 Dell computers on a wired network through a Linksys DSL router. Two of them are about 50 feet away from the router and the third one is next to it. I have no problem with the third computer, goes on-line fine with 100 Mbps NIC speed. The other two computers, I was able to make them get IP addresses from the router after setting the NIC's speed and duplex to 10 Mbps full. When set at default (Auto) they gave unpredicted results. Typing IPCONFIG will give either or IP addresses that didn't start with 192.168.1.x. When I set up one of these computers next to the router, then it works fine like the third computer. Do I have problem with weak signal? Could this problem be fixed by connecting them to a switch/hub from the router?

Any help is greatly appreciated.
Question by:joekasmijan
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LVL 16

Expert Comment

ID: 12210640
>Do I have problem with weak signal?

Sounds likely.

>Could this problem be fixed by connecting them to a switch/hub from the router?

I doubt it - is the short cable still fast when you plug it into one of the ports that the slow computers were using?

Are the ends on your cables hand-crimped, or did you buy machine-crimped cables?


LVL 20

Expert Comment

ID: 12210881

Assisted Solution

cagri earned 248 total points
ID: 12211090
Dear Joekasmijan,

I've read your message twice to see if I skip you were saying what happens if the two computers are set to 100Mbps/Full manually ??? Here are the possible reasons for your problem;

1. Auto mode !!! Let me briefly describe what is the auto mode. This is an extension on Layer 1/2 providing mutual negotiation of the bandwidth and duplex setting betten the network NIC and the Switching device. However, the protocol extension mentioned might be implemented slightly different between vendors and even when using well know brands on both sides, connectivity problems may arise. This is a know issue without a practical solution (other than manual settings).

The indications of mis-negotiation are slow trasfer speeds, time to time connection losses and lack of connectivity at all. The workaround is to set bandwidth and duplex mode manually to the same value on both sides.

In the linksys case, I don't think the device has individual settings for switch ports (mine does not have at least) so an option might be to set the computer NIC to 100/Full. If this not solve the problem one of the resons might be the both devices are still unable to negotiate. This might be dependent to NIC vendor also, could you please check to see whether the vendors/models of the NIC adapters are different or not.

Please do this test; exchange network NICs on near and far computers and observe the result, or you may unplug 50feet cable and plug it on the near computer (whichever one is easier for you), this is instantly show you whether it is NIC or the cable.

2. If you decide it is cable, you may need to replace, or re-crimp the cable. 50ft is a small distance if for consider 100BaseTX is certified up to 100m or 300ft. So if it is not the NICs something must be wrong with the cable. Please use a CAT5 or 6(category 5 certified cable), if you yourself crimping the cable, leave no un-twisted cable near the jacks. Or a better solution might be to purchase a factory crimped cable.

Hope this helps,
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Author Comment

ID: 12212782
Thank you to all of you.

>is the short cable still fast when you plug it into one of the ports that the slow computers were using?

Yes, a short cable on any port works good on any computer connected to it. To clarify further, I even connected my laptop to the 50 feet cables, I experienced the same problem.

>Are the ends on your cables hand-crimped, or did you buy machine-crimped cables?

I hand-crimped them my self.

>what happens if the two computers are set to 100Mbps/Full manually ???

I remembered it right, it gave me the same result (not able to go on-line)

>exchange network NICs on near and far computers and observe the result

The NICs are buit-in to the motherboard in all of them, they are Broadcom 440x.

I'll give it a try with factory-crimped long cable next week and let all of you know the result.
Thanks again.
LVL 16

Accepted Solution

The--Captain earned 252 total points
ID: 12213033
>>Are the ends on your cables hand-crimped, or did you buy machine-crimped cables?

>I hand-crimped them my self

Bingo.  You cannot trust hand-crimped cables, period.  I wish they would stop selling male RJ-45 ends - it implies that cables can be hand-crimped well, which is just not the case.

Case in point - I used to work for an ISP - we had intermittent troubles all over our network - finally, we got management to buy a decent cable tester and had one of the junior techs run through every single cable - 80% of our hand-crimped cables turned up bad in some respect, according to the cable tester(and how much you wiggled the cable).  We naver had to hand-crimp anopther cable again, since management allocated $$ for enough cables to replace all our hand-crimped runs, and quite a few extra to boot.

My suggestion - go out and buy one factory-crimped 50ft cable.  If that works (and I'm sure it will), you can then justify buying the second one.


Author Comment

ID: 12244939
Yo are right The--Captain and Cagri. I bought a 50 foot machine-crimped cable and it works like a champ. I have a feeling it depends on the NIC card also. I have been crimping long cables, over the ceiling and never had any problem until this Dell computer Broadcom 440x NIC. The reason why I said that, the guy that I do this work on, has another store in a different place that is having excatly the same problem (smae thpe of computers). Another tech installed the network couple years ago and he didn't even noticed the problem until I told him. I'll check if it is cable problem the next time I'm there. How should I split the points? 50-50?
LVL 16

Expert Comment

ID: 12245991
>Another tech installed the network couple years ago and he didn't even noticed the problem until I told him

Yup.  A cable will typically avoid being confirmed as out-of-spec until it is either tested with equipment that verifies it's electrical tolerances (a decent cable tester), or until it meets the wrong combination of equipment.  The problem is, an out-of-spec cable will work with lots of equipment, since a powerful ethernet tranceiver may be able to compensate for electrical deficiences in the cable - unfortunately, some equipment relies on having a cable that is completely electrically compliant (why else even bother to have a standard), and such equipment will fail (or perform sub-optimally) when presented with a substandard cable.

When I worked at the ISP, we had several hand-crimp tools - some would almost always produce crappy cables, some were about 50-50, and some produced mostly good cables - the point is *all* of them produced bad cables at some point, and there was no telling which were good and which were bad (you could tell the obvious really bad crimps just by looking, but that was about it) without a decent cable tester, and even then some of the good ones would go bad with sufficient wiggling.

The only consistent success I have had with hand-crimping is with those self-crimping modular patch panel jacks (you know, the ones that pop out of the chassis via plastic clips, and you can pry them apart with a flathead screwdriver by pressing on the release tab underneath).  Those seem to work since they have punch-block style connections that cut into and grab the wire in a perpendicular fashion (like a punch block) rather than relying on a single tiny copper blade to cut into and rest against the wire in a parallel fashion (as in a male RJ-45 end).  I keep a couple of those patch panel jacks in my laptop bag in case I need to quickly fashion a crossover cable (ethernet, T1, ATM) on-site.

> I have a feeling it depends on the NIC card also

I have no doubt of that - some NICs have more powerful transceivers than others

Take Nancy Reagan's advice and just say no to hand-crimped cables - you'll be glad you did in the long run.


P.S.  If you want to split pts 50-50, let me know - as PE, I can do it for you.


Author Comment

ID: 12251614
Thanks for all the info and advise regarding this matter. Now I know and learned something new. Yes, let split 50-50 and make everybody happy!
LVL 16

Expert Comment

ID: 12252423
No problem - I gave myself the 1 extra point (since it couldn't be split exactly 50-50) for doing the legwork.


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