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"splitting" Cat 5 cable

Last response: in Networking
November 24, 2001 1:38:14 AM

This is the scenario: We have a Netgear RT314 router to share our ADSL connection. I have teseted the setup withe both computers in the same room to verify functionality and it works perfectly.
However, the final setup will have the two computers on different floors, one near the router/DSL modem, the other downstairs. What we are going to do is run some CAT5 thru the walls by adding new RJ45 ports on wall-jacks. For the downstairs computer, there will be two hookup locations. My question is, can I run a single length of cable from one router port to downstairs and then "split" it, as so:

{with (1) and (2) being the two downstairs ports}

OR is splitting a cable mid-way not advisable for CAT5?
I know that the two downstairs ports won't be usable simultaneously, but that is OK. I just dont want any stability, speed, or connection problems.

The alternative is to make a separate run from two different router ports to the two downstairs ports, as so:

I prefer the first if possible (it uses less cable) but if any networking gurus know I should not "split" the cable, I will use the second solution. Any comment is appreciated!


More about : splitting cat cable

November 24, 2001 3:57:52 AM

Spliting cable can be done But I am an electriction and I just finished a job where they paid us big bucks to as they called it "fix it right" So I would not recomend it I ran cat 5 all through my house direct runs no splits and no regrets. Do it once do it right and you wont be sorry. Just my humble opinion

If you see a turtle on top of a fence post,
It's a good bet somebody, put him up there.
November 25, 2001 12:49:49 PM

Splitin isn't necessary! I have a similar setup - Router/Switch upstairs and two computers downstairs - with 1 Cat5 run! And I pulled the cat5 thru the existing phone conduit in the house, and put on coverplates with both RJ!! and RJ45 plugins. It does make a neat and convienient setup...

Cat5 is normally 4-Pair: Each Ethernet conection requires only 2 pair. You can easily run 2 2-pair eithernet connections thru 1 4-pair Cat5! It works fine and at 100mbs for a 50-60 yard run!

Ethernet uses only pins 1,2,3,6. Pins 1 & 2 are one pair, pins 3 & 6 the other pair! So its easy to get 2 ethernet LAN connections thru 1 4pair Cat5... Just insure pins 1,2 are 1 twisted pair and 3,6 are another twisted pair - or you'll only get 10mbs if not paired correctly...

Also i just noticed good ole Home Depot is now carrying RJ45 connections, plugs and coverplates. Pullin CAT5 in homes must be gettin commonplace...
I love my networked home...

Or you can get Cat5 in more than 4pair... Check Vance Baldwin Electronic( supply. Cat5 is made in 4,6,8,12,16 and more pair...
I can get 2 cat5 and 2 cat3 thru normal phone conduit, so 1-12pair Cat5 would be an easy pull...
Related resources
November 25, 2001 1:23:31 PM

For specs check out:

For the quickie, Eithernet only uses 2 pair(note: pins 4,5,7,8 aren't even used), so 2 eithernet connections with one 4pair Cat5 is easy!!!

*** 100BASE-TX Adapters ***

Cable and Connector Pinouts
If you need to repair a cable or provide connectors for UTP cable, wire straight through as shown in the following table.

Function Pin# Pin#

TX+ 1 <-----------> 1
TX- 2 <-----------> 2
RX+ 3 <-----------> 3
RX- 6 <-----------> 6

(This is an MDI, or straight through, cable).
Pins 1 and 2 must be a pair, and pins 3 and 6 must be a pair. The term "pair" refers to 2 wires, typically of a common color base, twisted around each other within the larger cable.

Pinout for the RJ45 connector (suggested wire colors)
---------- ------------------------------------------

1 |-- | 8 |brown or brown/white---|\
2 |-- | 7 |--white/brown----------| \
3 |-- ---- 6 |green or green/white---| \
4 |-- | 5 |blue or blue white-----| -
5 |-- | 4 |--white/blue-----------| _CABLE
6 |-- ---- 3 |--white/green----------| /
7 |-- | 2 |orange or orange/white-| /
8 |-- | 1 |--white/orange---------|/

---------- ---------------------------------------------
VIEWED FROM END VIEWED FROM TOP (opposite the retaining clip)

Pin Name and Function:

1. Transmit Data Plus (TD+): The positive signal for the TD differential pair. This signal contains the serial output data stream transmitted onto the network.

2. Transmit Data Minus (TD-): The negative signal for the TD differential pair. This contains the same output as pin 1.

3. Receive Data Plus (RD+): The positive signal for the RD differential pair. This signal contains the serial input data stream received from the network.

4. Not used.

5. Not used.

6. Receive Data Minus (RD-): The negative signal for the RD differential pair. This signal contains the same input as pin 3.

7. Not used.

8. Not used.
November 26, 2001 7:56:13 AM

Technically you can use the other 4 wires, but aren't you going to lose the electical interference cancelling capabilities of the UTP 10BaseT/100BaseTX specs if you do it?

<i>It's always the one thing you never suspected.</i>
November 26, 2001 3:55:56 PM

I'm using the "other 4 wires" - and No problem! Good Tx speed, and everything auto detects at 100mbs! Have two runs that way(thru existing phone conduit between floors). No prob...

I'm not a hardware, network guy, but network guys at work told me they don't have problems either... Works fine now, but if ethernet Tx protocol ever changes(or gets faster in future) ya might have to recable!

But for now, all's workin very well. If its not optimal I sure can't notice it... Usin a 8 port Linksys Cable/DSL router/switch, runs all thru the house, and it certainly seams to be as quick and any professional network i've worked on! Tis workin on my boxes!!!
November 28, 2001 11:10:03 AM

Cool. Thats good to know. Thanks.

<i>It's always the one thing you never suspected.</i>
November 29, 2001 7:55:25 PM

Then how is the color arrangement to make 2 100BaseTX UTPs using only 1 CAT5 cable?

And I want to ask another question outside the topic.
If 4 100BaseTX UTPs are connected through 1 UTP only (like in NJ100 case), doesn't it create a serious bottleneck?

<i>Most people thing that they are hunter, in fact they are hunted.</i> :eek: 
November 29, 2001 9:44:39 PM

I wired the RJ45 female plug-ins, inside the cover plates like this…
Same on both ends…

* Connection 1 …
1 - orange white
2 – orange
3 - green white
6 - green

* Connection 2…
1 – blue white
2 – blue
3 – brown white
6 – brown

It’s working for me… NICs all auto detect at 100Mbps…
I’ve never actually checked/measured my network transfer performance, but it sure feels right compared to my old 10baseTx hub setup… and the 100tx light on the Linksys router/switch is on… I’m a programmer, not a network specialist – All I wanted is a reliable network at home – and it’s working well…

Bottle necks??? Not that I know of…
June 3, 2009 8:07:24 PM

You can "split" cat 5 cable and it will work as stated many times above.
But what you might want to keep in mind is that this will prevent you from using
that cable for anything but 10/100 base T.

1000 base T , uses all the wires in the cable. Also if you ever wanted to use POE (power over Ethernet)
again uses the extra pairs for the power.

The best alternative would to pull 2 cables. The next best thing would to get a cheap switch and do it that way. You can find them now for around $10.00

July 30, 2009 7:40:45 PM

well, to reinforce there are people out there looking for such splitting, we have a camera image that for reasons of redundancy/archival, would be quite useful to get into 2 different subnets. The CAT5 comes directly from the camera into the control room, where there are the 2 different subnet switches. One subnet is IT side, the other "plant control".
February 27, 2011 11:16:37 PM

I wanted to attempt this for a test and I'm having problems understanding.

I wired on the 1 modular plug side.

1- orange white
2- orange
3- green white
6 - green

2nd modular plug I wired

1- blue white
2- blue
3 - brown white
6- brown

then on the patch panel, do i map the colors the same way?
February 28, 2011 12:10:33 AM

No, on the patch panel for port 1 you need to do things like normal, the second plug put the blue wires on the orange color, and the brown on the green. That way your on pins 1,2,3,6 on both ports on the patch.
June 17, 2011 7:55:02 PM

Bob, you said:

"1000 base T , uses all the wires in the cable. Also if you ever wanted to use POE (power over Ethernet) again uses the extra pairs for the power. "

That's only half correct. According to 802.3af, running 10/100 in mode "a" you will have POE on the original "channel" assuming the POE source device and client device are 10/100 devices, ie;, the switch is a 10/100 switch, and since presumably you would be plugging the second "channel" (brown/blue in the home run) into another port on the switch you would have POE there as well... assuming you've got the polarity correct in your adapters.

I am not sure whether a gigabit switch and/or client device is smart enough to change the modes when auto-detecting a 10/100 connection, some may be and others may not. I would tend to think they should be since the POE is shifted from 1/2 & 3/6 to 4/5 & 7/8 in gigabit "b" and back to 1/2 & 3/6 again for gigabit "a".

I guess the "admiral's test" would be to simply cut the brown and blue pairs in a patch cable, plug it in and see if that AP or phone still works.

I have always carried around a pair of "Y" cables in my laptop case for those times I need to plug in next to a client computer. Much easier than lugging around a 4-port switch with two cables and then finding a place to plug in the wall wart without killing something else or disturbing the rat's nest of dusty, tangled wiring under the client's feet. It's also a handy and quick solution when adding a printer or laptop port in somebodies cubicle... definitely better than installing a soon to be forgotten and/or undocumented switch, assuming you have the real estate on the main switch, and even then if I had to add a switch I would prefer to add it and maintain it back with the other network hardware where I and the next guy can see it. I have also used it when people needed to connect up a modem and had no phone line, as well as people who had phones on Cat5 with no extra run for data... 10/100 plus two copper in minutes. As an old RF guy I am sure you appreciate the elegance of good old fashioned twisted pair when it comes to common mode rejection, whether blending digital and analog signals or feeding that 1/2 wave doublet... ahhh, but you are into 3/4 meter CB and Heliax, not HF, but I digress.

Besides, it only takes about five minutes to cut two patch cables in half, dress the ends and crimp them into two RJ45 plugs, so I'd rather do that on the spot than run out to Best Buy for a switch or tell the customer they'll have to wait and pay for a new run to be jerked... that can come later after they have a full days cable work queued up or a major upgrade. But that's just me. I'm Scottish.

June 19, 2011 12:47:45 AM

This topic has been closed by The_Prophecy