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weird behaviour with a 50m CAT5 cable run

Posted on 2004-11-19
Medium Priority
Last Modified: 2013-11-09

i have a D-Link DSL-5004 modem/router and a DWL-2100AP wireless access point

the modem/router sits in my office and the WAP is supposed to be at the end of a 50m (absolute max - probably less) CAT5 cable run into the house (rj45 each end)

with the WAP and centrino laptop in my office, and the WAP connected to the router with a standard 1m patch cable, everything works

with the laptop connected directly to the rj45 at the house end of the long run and the office end to the router, everything works


with the WAP connected to the house end of the run and the router to the other - nothing works!!

in all cases the Link LED on the router is lit providing the long run is plugged into something at the far end

when the WAP is plugged in at the house end (ie: 3 above) the LAN LED, which should be solid lit without packets, flashes regardless !?!

the cable was made up by an electrician and is standard CAT5 solid core AFAIK

any ideas as to why this should happen and/or what to try?


Question by:babysnake
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Expert Comment

ID: 12628188
The only thing I can think of is maybe you need a crossover cable to do this, or an uplink port on one of the devices.

Author Comment

ID: 12628294
i tried a short x-over cable in the office and the WAP worked no probs

does it matter exactly the order of the coloured wires in the rj45 pins?

mine is (pin 1 first)

white/brown/white/blue/white/green/white/orange  AFAI can see


Expert Comment

ID: 12628447
The order should not matter as long as it the same on both ends for a straight cable.  If looks like you cable was made to follow 568B standards.  I would check both devices for an uplink port.  If one of them has one, just plus the cable into that port.  Some devices will automatically detect if the port needs to be an uplink port or not, but it sounds like your devices do not do this.  Another alternative is to but a cheap switch that does automatically detect this and run hook the cable into this and run another cable from the switch to the router.  Hope this helps.
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Expert Comment

ID: 12628757
in x-over cable only two wires replace each other. Send and receive.

Accepted Solution

Hakim earned 580 total points
ID: 12628966
the colour coding of wires in twisted pair are as follows:

1. white & green
2. green
3. white & orange
4. blue
5. While & blue
6. Orange
7. White brown
8. Brown

in a straight cable both end has the same colour while x-over the orange and green swap place at the other end.


Expert Comment

ID: 12629474
Can you verify the model number of your router.  I could not find a D-Link DSL-5004 router on D-Links web site.  It is possible to change the cable into a cross-over cable but I would avoid that.  It's working fine as a straight cable and I woudl generally not mess with something thats working correctly.   An uplink port on your router is the best method to connect, if one is there.  If I can find your router on the web I can probably tell you exactly what you need to do.  Otherwise for under $40.00 you can get a switch that has auto-sensing MDI/MDIX, or uplink, ports.

Author Comment

ID: 12630541
sorry i gt the model wrong !

it's a DLink 504 router

in fact now i look at the cable colouring it's neither a 568a nor b standard, rather something else. it clearly works after a fashion, it's just a bit marginal (to steal someone else's term!)

i'll have it recrimped to a proper standard and let you know if that works

thanks for the input



Expert Comment

ID: 12631312
When the led flashes constantly on an ethernet port  it is a sign that cabeling is not OK it is IMPORTANT to use the right wire order (use the one above from HAKIM). It is no problem if the cable is short 2m... but when you have longer cable then there is a lot of interference betwen wires so the switch or router with switchports disables that port (led is red or flashes) or eaven blocks the whole switch.

Try cutting off both rj45 connectors and connect new ones using wiremap from HAKIM.

Expert Comment

ID: 12631546
Since the cable has been working a senario 2 above, and the fact that they worked together with the crossover cable,  I don't believe there is anything wrong with the cable excpet you are now connecting to hubs together and need it to be a crossover.  I did some research on your products and it looks liek they do in fact need a crossover cable between them.  On most devices you will nto get a link light if you are using the wrong type of cable.

 I also agree that following wiring standars is good.  Hakin gave you the layout for 568A.  Here is a web site that lits both 568A and 568B.  


Here is a web site tat says how to wire corssover cables.

Let me know if this help.

Expert Comment

ID: 12640585
I don`t think this was said, if it was then sorry.

You should also make sure that the cable is shielded.
Using such a long unshielded cable running along walls with other wiring within them is never a good idea.

Author Comment

ID: 12645603
sorry for th delay!

the electrician rewired the cable according to Hakim's scheme and - tada! - it all works :)

thanks for the input and education


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