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network connection

Posted on 2000-05-16
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Last Modified: 2008-02-01
Hardware used: AMP Enhanced cat5 cable (10 metre in length) , D-link DFE-916Dx 10Base-T/100Base-tx Dual speed hub, D-Link Dfe-538TX 10/100 Adapter.

Problem faced: I am unable to connect our station with 100Mbps if the cable exceeds 10 Metres, howeever it runs smoothly with the cable length shorter than 6 metres. For cable length longer than 6 metres it can run at a speed of 10Mbps.

Solution needed: How to stack up data signal to enable it to run at 100Mbps?
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Question by:paullim
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12 Comments
 
LVL 13

Expert Comment

by:magarity
ID: 2816083
Wow, only 10 meters?  The specification allows cables to be up to 100 meters.  Still, you're apparently picking up interference from somewhere that is preventing a clean signal at high speed.

OK, what to do about it?

Suggestion 1: Check along the path of the cable to look for anything that might be causing this interference.  Make sure there are no loops or knots in the cable.  Is this in an office building?  See that the cable doesn't wind past: Electrical wires, other computers or monitors, televisions, refrigerators (water coolers), phone PBX trunk lines.  The problem is that a major trunk of electrical cabling might be hidden behind the wall and that might cause enough interference.  You'd never see it.

Suggestion 2: * IF * the hub is right next to one of the computers:  Can you simply relocate your existing hub so that it is nearer to in between the two machines?  The hub can go anywhere, unless you really want to watch the little lights flicker.  If the hub is in between the two machines instead of next to one of them then there would only be 5 meters on each side.

Suggestion 3:  If all the above fail, you can get a repeater.  This is a device like a hub , except all it does is amplify the incoming signal and pass it on.

Additional questions you might answer to help narrow things down: When you tested with 10 meters, was the cable stretched out along the path you expect it to lie or was it all tangled up with the two computers next to each other?

Is it at all possible to string the cable so that it ISN'T against walls or even floors (from top to top over cubicles?) to eliminate the possibility of an electrical trunk hidden in the wall/floor?

Have you tested against the possibility that this 10M length of cable itself is bad?  There could be an internal break somewhere and you'd never know.
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Author Comment

by:paullim
ID: 2816524
suggestion 1: No interference at all, because we locate the problem then we try with cables of different type ie D-link, Lucent, AT&T, delben, AMP enhanced cable (all new cable, on the floor, well placed).

Suggestion 2: Our server room in at the corner of 3rd floor, even if we shift the server room to the middle of the room, it will be exceeding 10 M to connect to pcs in 2nd floor.

Suggestion 3: I have not try this, may be is a help, please more clearly explain the function of the repeater and the cost, brand etc? so that I will try to get one. Thanks

The possibility of the cable being 'bad' is near to Zero.

Welcome more suggestions and help.

Thanks very much
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LVL 2

Expert Comment

by:jj_mako
ID: 2817500
i have been through this.

what i found:

the cable isn't paired correctly.  there are 8 conductors for each connection.  the conductors are divided into 4 pairs. these pairs are twisted together.  in many cases when you look at the end you'll see the pairs in order, for example:

white/orange, orange, white/green, green, white/blue, blue, white/brown, brown.

this is wrong.

this is correct:
white/orange, orange, white/green, blue, white/blue, green, white/brown, brown.

if you notice, the green pair is split between 3 and 6.  this needs to be done to get 100MB.  it will work great on 10 but it will not work at 100.

i hope this helps, it's a bit confusing.
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LVL 13

Expert Comment

by:magarity
ID: 2817724
>if you notice, the green pair is split between 3 and 6.  this needs to >be done to get 100MB.  it will work great on 10 but it will not work at >100.

Mako,

I don't understand:  "it needs to be done to get 100 ... but it will not work at 100."


What is "it" and what needs to be corrected about the green wires?

paullim,

if you can figure out how to adjust your cable by mako's suggestion, it sounds like there might be something to it.

If that still doesn't work:
A repeater, as I mentioned, reamplifies the incoming signal and passes it on.  When the signal degrades because of interference or cable length the repeater just refreshes it to the same strength and cleanliness as when it came out of the network card.

It looks from the model of hub and network cards you list that you got one of D-Link's prepackaged everything-you-need network setups.  D-Link makes decent hardware, but they put their lowest end models in those bulk packs.  Their DFE line of hubs are not switchs or repeaters.  Compare to their DSS line:

http://www.dlink.com/products/switches/dss8plus/

Scroll down to where it says 'standards compliance'.  Notice that this model is a 'IEEE 802.3u 100Base-TX Class II Fast Ethernet repeater.'  The DFE hubs do not meet this spec on Dlink's website.  So, *IF* the problem you are having is indeed a case of signal degradation (because of interference) then this switch instead of your hub would do the trick.

The DSS 8+ (8 ports) starts at $82 mailorder.  There are also 5, 16, and 24 port  in the DSS line depending on how many ports you need.

Here is a link to a mailorder place selling all four sizes:
http://www.comready.com/switches.html

Note: I have never ordered anything from this vendor and have no recommendation about them either way.

If you got this setup at a local retailer, ask if you can borrow a DSS 8+ to see if it does indeed solve your problem.   I'd suggest that you check with the vendor where you got the setup you have now to see about an upgrade trade-in.  

If you don't get any better suggestions, try one of these switches.  If you get one mailorder get one from somewhere with a lenient return policy just in case I have no idea what I'm talking about (happens rarely, but it does happen!).

A reason to upgrade to a DSS series switch even if you solve your problem some other way:  I went from a simple switch like your DFE to a DSS 5+.  Under the old hub Win98's system monitor reported 700-800 kbytes per second (I have all 10mb cards but the DSS is 10/100) of network traffic.  With the DSS this number jumped to 1100-1200.  This is becase the DSSes are buffered switches instead of hubs.

regards,
magarity
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LVL 2

Expert Comment

by:jj_mako
ID: 2817943
it's kinda hard to explain, if we had the wires and connectors in front of us, it'd be a piece of cake.

look at the rj45 male connector, the side without the tab.  with the cable at the bottom look at the colored conductors inside.  from left to right they should be:

white/orange, orange, white/green, green, white/blue, blue, white/brown, brown

now this is industry standard, whoever cabled it may NOT have used this color scheme.  what is important is that the third conductor and the sixth conductor are the same pair.

now, this cable sequence must be maintained throughout the length of the cable.  open the box that the cable plugs into on the wall (if it has one) and look at the cable sequence, it must be the same. conductor 3 and 6 are the same pair.  now you need to check the distant end, make sure that the same sequence is repeated.
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LVL 12

Accepted Solution

by:
mark2150 earned 100 total points
ID: 2818947
jj_mako You've got it bass-dackwards!

W/Orange
Orange
w/Green
Blue
W/Blue
Green
W/brown
Brown

This is ATT 568B standard pin out. Hold connector w/clip down, cable exiting to left and this is order of colors. Should be same-same at both ends.

While the chances of a bad cable are low, it is quite possible you have a bad NIC connector. Swap out the NIC and see if problem clears.

DO NOT install a repeater in an attempt to correct this. There is a problem somewhere that installing a repeater will only mask. 100BaseTX will go more than 10M without problem if properly installed.

Cables need to be Cat-5 tested/certified, not just "compatible".

Twist needs to be maintained within last 1/2" or less.

M
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LVL 2

Expert Comment

by:jj_mako
ID: 2819092
you're right mark, i cut and pasted from my first comment, i only did the wrong one, thanks for the correction.
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LVL 2

Expert Comment

by:jj_mako
ID: 2819186
i did a quick search and found these pictures, this will explain it better, it's got colors!

use the 568b configuration.


http://www.monmouth.com/~tson/tbs/network.html

http://hepunx.rl.ac.uk/ppncg/utpguide/page18.html
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LVL 13

Expert Comment

by:magarity
ID: 2819301
paullim says he has tried with 5 different brands of cable including Lucent, so I really doubt that it is an improperly made cable.  (unless it was bulk cable and you put your own ends on it?)
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LVL 12

Expert Comment

by:mark2150
ID: 2819880
yeah, but *connector on NIC* could have bent pin!

M
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Author Comment

by:paullim
ID: 2820107
Thanks so much. At last I got the answer through your assistance!
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LVL 12

Expert Comment

by:mark2150
ID: 2821009
Glad to help. Thanx for the points!

M
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