I have a problem. I recently bought a new house that was "wired for a home network". Well, it turns out that their idea of wired is throwing a Cat 5 line into the wall, using a pair for the phone and leaving the rest for the homeowner to figure out when/if they want a network.

So, here is where I am right now. I know that you can use only 2 twisted pair for wiring and that they have to use pins 1,2,3 and 6. I have hooked the wires to the punchdown in the basement. (I only had room for a total of 3 pairs on the punchdown...1 pair for the phone, 2 pairs for the network) I wired a rj45 jack into the punchdown (using pins 1,2,3 and 6). I then wired a quick-connect style rj45 jack in an upstairs bedroom (using pins 1,2,3 and 6).

Now, when I connect everything I have no connection. I cannot figure out why. I have checked all of my connections and they seem fine. If pairs are untwisted too far will that cause the connection to not work? Or will it just make the signal weaker? Is there something I missed in wiring it up? Anyone have any other ideas? :confused:


Posted on 2003-11-18 08:03:31 by bo_monster
I think that the cable resitance is to big ,it depends on how is the cable long.
Long time ago I linked 2 PSs by rj45(must be crossing) without any success.
When I had shorter connection everything was OK.
When I increased a distance between hosts then connection was impossible.

I got off the crossing cable and changed it with two rj45 link and hub between the hosts.

The hub pick up the signal and link started to work properly.
So maybe you have the same problem.

Posted on 2003-11-18 08:15:16 by HarryTuttle
I doubt that you exceeded the maximum segment length.

Did you properly pair your connections?

For straight through cabling, which is what you use to connect between a PC and a hub/switch, is this:

Color / Stripe

1 ----- White / Orange ----- 1
2 ----- Orange / White ----- 2
3 ----- White / Green ----- 3
- -
- -
6 ----- Green / White ----- 6
- -
- -

Pins 1 and 2 MUST be on one twisted pair, and Pins 3 and 6 MUST be on another twisted pair.
The twists in the cable are important to the operation of Ethernet.

What do you have connected to each end? Is it PC to hub?
Do you have any crossover cables in the link.
Posted on 2003-11-19 23:49:47 by eet_1024
For reference i'll let you know I had to use the Brown pair and Green pair (because of the way the home builder used the other pairs).

Basically I have a cable modem in the basement, hooked to a router, which is then hooked to a jack that is hooked to the punch down.

The punch down is wired to the rest of the lines using the same Brown and Green pairs.

Upstairs I wired an rj45 jack using the Brown and Green pairs and being sure to use pins 1,2,3 and 6 in the same color order as downstairs. One thing I did noice that was wierd was that if I hooked the modem to the jack upstairs and the router to the jack in the basement I saw a signal on the router from the modem (?) But if I hook it up the way I want to I don't get a signal from router downstairs to PC upstairs.

Ok, I hope that explains my situation a little better.


Posted on 2003-11-20 10:07:13 by bo_monster
Sounds like your connecting the punch down to an uplink port on the router.

Connect the router to the punch down with a cross over cable.

All you have to do to make a cross over cable is swap 1 with 3, and 2 with 6. Keep Strips on odds, and Solids on evens.
Posted on 2003-11-20 23:28:08 by eet_1024
Cat 5 cable has to have a certain number of winds per foot. The capacitance of the cable is affected by this and it is important to try to minimize any unwinding (it creates an induction in the cable to counter the capacitance). The way Cat 5 works is it is coated to reduce the "skidding" affect of electrons where when the frequency gets too high the electrons tend to travel on the outer part of the conductor near the surface of the cable. It also requires a certain number of twists per foot as the capaciitnce of the cable must be very close to the same for all pairs, capacitance and resistance will combine to delay a signal and can reduce the bandwidth of your cable as there will be more out of sync data on different pairs as one signal arrives shortly before another. So try not to unwind your cable and minimize any exposure of the cable's conductor to the air where it can be scratched. Cat 5 cable can be run a long way before there is significant reduction in performance, it is unlikely that the cables length is a factor in your problem.
Posted on 2003-11-20 23:38:12 by donkey
Can you think of any reason why the Router and modem will communicate but the PC will not communicate with either? I already have the setup within the office (which does function very well), I am just basically adding a connection in between them. I checked the wind for each pair and made sure to rewind any unwound sections. Still no go. At least I know there isn't a break in the connection since the router and modem communicate.
Posted on 2003-11-21 08:52:36 by bo_monster
Generally routers and modems require a straight through connection while PC's require a cross over. Check the wiring diagram for your devices or use a short cable that works for each and copy that.
Posted on 2003-11-21 09:08:00 by donkey