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Building Your Own Twisted Pair Cables

LAN 102: Network Hardware And Assembly
By

When it’s time to wire your network, you have two choices. You can opt to purchase prebuilt cables, or you can build your own cables from bulk wire and connectors.

You should build your own twisted pair (TP) cables if you:

  • Plan to perform a lot of networking
  • Need cable lengths longer than the lengths you can buy preassembled
  • Want to create both standard and crossover cables
  • Want to choose your own cable color
  • Want maximum control over cable length
  • Want to save money
  • Have the time necessary to build cables


While you can save money building your own cables, you can get pre-made network cables at very low prices from some online vendors such as MonoPrice (www.monoprice.com). In many cases you’ll find that it is actually cheaper to purchase pre-made cables than it is to build your own.

TP Wiring Standards

If you want to create TP cables yourself, be sure your cable pairs match the color coding of any existing cable or the color coding of any prebuilt cabling you want to add to your new network. Because there are eight wires in TP cables, many incorrect combinations are possible. Several standards exist for UTP cabling.

Tip: The key is to be consistent. Use the same scheme for all your cables, and ensure that anyone else working on your network understands this scheme.

The most common standard is the AT&T 258A configuration (also called EIA/TIA 568B). The following table lists the wire pairing and placement within the standard 8P8C (RJ45) connector.

8P8C (RJ45) Connector Wire Pairing and Placement for AT&T 258A/EIA 568B Standard
Pin
ColorPair
1
Orange/White2
2
Orange2
3
Green/White3
4
Blue1
5
Blue/White1
6
Green
3
7
Brown/White
4
8
Brown4

*This pair is not used with 10BASE-T or Fast Ethernet 100BASE-TX, but all four pairs are used with Fast Ethernet 100BASE-T4 and gigabit Ethernet 1000BASE-TX standards.

In the following image, an 8P8C (RJ45) cable connector is wired to the AT&T 258A/EIA 568B standard.

An AT&T 258A/EIA 568B standard–compliant 8P8C (RJ45) connector.An AT&T 258A/EIA 568B standard–compliant 8P8C (RJ45) connector.

Note: You also might encounter the similar EIA 568A standard. It reverses the position of the orange and green pairs listed previously.

Crossover UTP Cables

Crossover cables, which change the wiring at one end of the cable, connect two (and only two) computers when no hub or switch is available or connect a hub or switch without an uplink port to another hub or switch. The pinout for a crossover cable is shown in the table below. This pinout is for one end of the cable only; the other end of the cable should correspond to the standard EIA 568B pinout, as shown in the previous table.

8P8C (RJ45) Connector Wire Pairing and Placement for EIA 568A Standard
Pin
ColorPair
1
Green/White3
2
Green3
3
Orange/White2
4
Blue1
5
Blue/White1
6
Orange
2
7
Brown/White
4
8
Brown4

Note: Most standard cables have both ends wired using the EIA 568B standard, however it is also possible to wire them with both ends using the EIA 568A standard. As long as both ends are wired the same in a straight-through configuration, the cable will work. Crossover cables should have one end in an EIA 568B configuration, while the other end is in an EIA 568A configuration, thus crossing pairs 2 and 3. It should be noted that other wiring schemes exist for connecting UTP cables with 8P8C (RJ45) connectors. The ones listed in this chapter are the most common.

Most newer switches are designed so as to automatically detect whether a crossover connection is required and configure the connection appropriately. This feature is called Auto-MDIX (automatic medium-dependent interface crossover) and essentially negates the need for having dedicated “uplink” ports or using crossover cables when connecting devices together.

Constructing the Cable

Making your own network cables requires a few tools that aren’t found in a typical toolbox. Those items that you might not already have you can typically purchase for a single price from many network-products vendors. You need the following tools and supplies to build your own Ethernet cables:

  • UTP cable (Category 5 or better)
  • 8P8C (RJ45) connectors
  • Wire stripper
  • 8P8C (RJ45) crimping tool


Before you make a “real” cable of any length, you should practice on a short length of cable. 8P8C (RJ45) connectors and bulk cable are cheap; network failures are not. Follow these steps for creating your own twisted-pair cables:

1. Determine how long your cable should be. You should allow adequate slack for moving the computer and for avoiding strong interference sources. Keep the maximum distances for UTP cables of about 100 meters in mind.
2. Roll out the appropriate length of cable.
3. Cut the cable cleanly from the box of wire.
4. Use the wire stripper to strip only the insulation jacket off the cable, exposing the TP wires (see the figure below); you’ll need to rotate the wire about one and a quarter turns to strip away all the jacket. If you turn it too far, you’ll damage the wires inside the cable.

Use the wire stripper to strip only the insulation jacket off the cable.Use the wire stripper to strip only the insulation jacket off the cable.

5. Check the outer jacket and inner TP wires for nicks; adjust the stripper tool, and repeat steps 3 and 4 if you see damage.
6. As shown in the image below, arrange the wires according to the EIA 568B standard. This arrangement is listed previously, in the section “TP Wiring Standards.”

Arrange the wires according to the EIA 568B standard.Arrange the wires according to the EIA 568B standard.

7. Trim the wire edges so the eight wires are even with one another and are slightly less than 1/2-inch past the end of the jacket. If the wires are too long, crosstalk (wire-to-wire interference) can result; if the wires are too short, they can’t make a good connection with the 8P8C (RJ45) plug.
8. With the clip side of the 8P8C (RJ45) plug facing away from you, push the cable into place (see the image below). Verify that the wires are arranged according to the EIA/TIA 568B standard before you crimp the plug onto the wires (refer to the previous table further up this page). Adjust the connection as necessary.

With the clip side of the 8P8C (RJ45) plug facing away from you, push the cable into place.With the clip side of the 8P8C (RJ45) plug facing away from you, push the cable into place.

9. Use the crimping tool to squeeze the 8P8C (RJ45) plug onto the cable (see the image below). The end of the cable should be tight enough to resist being removed by hand.

Figure 17.13: Use the crimping tool to squeeze the 8P8C (RJ-45) plug onto the cable Figure 17.13: Use the crimping tool to squeeze the 8P8C (RJ-45) plug onto the cable

10. Repeat steps 4–9 for the other end of the cable. Recut the end of the cable if necessary before stripping it.
11. Label each cable with the following information:

  • Wiring standard
  • Length
  • End with crossover (if any)
  • ________ (a blank) for computer ID


The cables should be labeled at both ends to make matching the cable with the correct computer easy and to facilitate troubleshooting at the hub. Check with your cable supplier for suitable labeling stock or tags you can attach to each cable.

Cable Distance Limitations

The people who design computer systems love to find ways to circumvent limitations. Manufacturers of Ethernet products have made possible the building of networks in star, branch, and tree designs that overcome the basic limitations already mentioned. (For more information, see the “Wired Network Topologies” section later in this chapter.) Strictly speaking, you can have thousands of computers on a complex Ethernet network.

LANs are local because the network adapters and other hardware components typically can’t send LAN messages more than a few hundred feet. The table below lists the distance limitations of various types of LAN cable. In addition to the limitations shown in the table, keep the following points in mind:

  • You can’t connect more than 30 computers on a single Thinnet Ethernet segment.
  • You can’t connect more than 100 computers on a Thicknet Ethernet segment.
  • You can’t connect more than 72 computers on a UTP Token-Ring cable.
  • You can’t connect more than 260 computers on an STP Token-Ring cable.
Network Distance Limitations
Network AdapterCable TypeMaximum Minimum
Ethernet10BASE-2185 m (607 feet)0.5 m (1.6 feet)
10BASE-5 (drop)50 m (164 feet)2.5 m (8.2 feet)
10BASE-5 (backbone)500 m (1640 feet)2.5 m (8.2 feet)
10BASE-T
100 m (328 feet)2.5 m (8.2 feet)
100BASE-TX100 m (328 feet)2.5 m (8.2 feet)
1000BASE-TX100 m (328 feet)2.5 m (8.2 feet)
10GBASE-T
100 m (328 feet)2.5 m (8.2 feet)
Token Ring
STP100 m (328 feet)2.5 m (8.2 feet)
UTP45 m (147 feet) 2.5 m (8.2 feet)
ARCnet
Passive hub drop
30 m (98 feet)Varies by cable type
Active hub
600 m (1968 feet)
Varies by cable typ


If you have a station wired with Category 5 or better cable that is more than 328 feet (100 meters) from a hub, you must use a hub or switch that acts as a repeater to regenerate the signal. If you have two or more stations beyond the 328 foot limit of UTP Ethernet, connect them to a hub or switch that is less than 328 feet away from the primary hub or switch and connect the new hub or switch to the primary hub or switch via its uplink port. Because hubs and switches can act as repeaters, this feature enables you to extend the effective length of your network.

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  • 5 Hide
    JasonAkkerman , November 2, 2011 4:37 AM
    Lots of good information there. Lots of history too.
  • 0 Hide
    KelvinTy , November 2, 2011 7:45 AM
    O... I thought all CAT5 are able to transmit 1000Mbps signals BEFORE reading this article... It's kind of weird ~_~" that I can get 5.X MB/s download speed = ="
  • 4 Hide
    Reynod , November 2, 2011 10:28 AM
    Don could you talk to Chris A and Joe and see if we could give a few hard copies of this book away as prizes for some of our users here in the forums who work hard to help others?

    How about a copy for each of the users who make the top ranks for the month of November ... under the Hardware sections of the forums?


    :) 
  • 0 Hide
    Anonymous , November 2, 2011 1:12 PM
    mixer device
  • 2 Hide
    JasonAkkerman , November 2, 2011 1:18 PM
    They make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.
  • 0 Hide
    thrasher32 , November 2, 2011 1:45 PM
    Great information.
  • 0 Hide
    xx_pemdas_xx , November 2, 2011 1:57 PM
    JasonAkkermanThey make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.

    I got talked into making 10...
  • 1 Hide
    spookyman , November 2, 2011 2:11 PM
    JasonAkkermanThey make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.


    Oh I don't know. I have made several thousand patch cord over the past 18 years.

    All you need is a high quality crimper, good cutters and small screw driver. You are set.
  • 2 Hide
    silveralien81 , November 3, 2011 2:56 AM
    This was a great article. In fact it inspired me to buy the book. I'm happy to report that the rest of the book is just as well written. Very educational. A top notch reference.
  • 2 Hide
    neiroatopelcc , November 3, 2011 10:27 AM
    Read the first page. Seems like well written stuff, but not exactly written for my type of user. Also it seems to be igoring a lot of stuff. For instance it sais the network runs at the speed of the slowest component and will figure it out on its own. This isn't true. If you run a pair of 1000TX capable nics on old cat 5 cable (without the e), it'll still attempt to run at that speed, despite the massive crc errors it might generate. Also, if you're running on 'old gigabit hardware' it won't nessecarily have support for 10Base-T speeds. Also, not all firmware has autonegotiate or automdix support, thus you sometimes have to specificly set the speed between links. This is mainly for fiber links though, which seem to have been ignored entirely.

    Anyway. As I said, I think it's well written and probably quite suitable for people who don't know anything about networks (except it seems to assume people know the osi model). I'll go see if the other chapters are equaly basic.
  • 0 Hide
    fixxxer07 , November 4, 2011 1:28 AM
    kelvintyO... I thought all CAT5 are able to transmit 1000Mbps signals BEFORE reading this article... It's kind of weird ~_~" that I can get 5.X MB/s download speed = ="


    5 MBps = 40 Mbps... so it's not that weird. xD
  • 0 Hide
    dthurber , November 4, 2011 2:00 PM
    Great article with lots of information. The crossover cable mentioned would work for 10/100, but for gigabit ethernet you must also crossover the blue and brown pairs. Unlike 10/100 ethernet, gigabit ethernet uses all eight conductors.
  • 1 Hide
    cangelini , November 4, 2011 7:59 PM
    reynodDon could you talk to Chris A and Joe and see if we could give a few hard copies of this book away as prizes for some of our users here in the forums who work hard to help others?How about a copy for each of the users who make the top ranks for the month of November ... under the Hardware sections of the forums?


    Heya Reynod,

    We had access to 10 copies of it for a contest that ran with the first few pieces of the book, but those were given away already.

    I agree that it's a great idea to reward the most active forum users, though. I'll get together with Joe and see if there's anything we can do there!

    Have a great weekend,
    Chris
  • 0 Hide
    Reynod , November 6, 2011 11:28 AM
    Thanks Chris.

    I feel a bit stupid now I missed it.

    It would be great if you could do something again though.

    I did PM Don Saturday to ask him.

    Cheers

  • 0 Hide
    neiroatopelcc , November 21, 2011 6:06 AM
    patch cables of those small lengths you just buy readymade - they're more sturdy anyway, and you can get them as any cable type (cat5e, 6a etc) .. and long's you don't add old cat5 or mix shielded with unshielded, cables really are the least difficult part of network building - although cisco want you to believe otherwise.
  • 0 Hide
    juanc , November 25, 2011 2:18 PM
    completely amazed at how many errors are in page 2
  • 0 Hide
    juanc , November 25, 2011 2:33 PM
    Either I'm missing to read something or the article on page 3 does not note, that to make Patch Cables you must use a different type, multi-filament copper cable instead of the standard in-wall one-wire solid copper conductors that get cut when you crimp. Huge mistake
  • 0 Hide
    juanc , November 25, 2011 2:44 PM
    Shielded twisted pair (STP) refers to the amount of insulation around the cluster of wires

    There is no "amount" it does have a shield.

    it was first thought that shielding the cable from external interference was the best way to reduce interference and provide for greater transmission speeds. However, it was discovered that twisting the pairs of wires is a more effective way to prevent interference

    No. Shielding is better. But the trick on twisting is that we are talking about "differential" signals. If not, twisting would be useless. Twisting to cables cancel each others emissions and emissions from other places to the cable are canceled too.

    10GBE pros say you should not wire UTP but only STP.

    Need cable lengths longer than the lengths you can buy preassembled

    Never buy preassembled cables. Can't assemble cable as I said before on mono-filament cable.
    One filament wires can't be twisted or take turns or >90 degrees. There's a big chance they can break. Can't wire thru a pipes with the RJ45 plug on it.

    Use Jacks. Buy machine assembled/tested multi-filament patch cords from the jack to the computer/router/printer/switch, whatever.
  • 0 Hide
    Slothy , January 13, 2012 11:57 PM
    I read this article as it was linked in the power supply guide posting, which I thought (on perusing it quickly) seemed rather well done. However, this article is so attrocious (both in inaccuracies and it's horribly outdated information) that it draws into doubt the quality of the original article that brought me here. I'm not just some Joe going off on a rant without knowing a thing, and my apologies as I am sure that this was likely intended for average Joe who doesn't have a strong base in networking, but even for that, it could have been written immensely better. I don't know if the author is to blame or the technical editor.

    First off, as a disclaimer, I didn't bother reading the wireless section. Stuff has been changing too rapidly the past few years to even bother, and it is ultimately so simple nowadays that you shouldn't even have to bother with the wireles options. What I did see of wireless information (such as range) was horribly inaccurate. In my experience with most indoor environments, you'll be lucky if you get a *reliable* signal at a fraction of the 150 feet he mentions.

    Simple advice for wireless: Buy a dual-radio N-capable wireless router and then decide if you're going to use N-capable internal wireless cards or USB dongles for any devices you have that do not include integrated wireless. Be warned that in my experience, many wireless routers designed for home use work fine for wireless devices accessing the internet, but when attempting to transfer data between a wired and wireless device, the router will act as a bottleneck, often running at speeds lower than what standard (10 Mbps) ethernet will provide. If you plan on hooking up a device such as a home server or NAS device to your home wireless router, be careful what you pick and either fork out the money for a higher-end SOHO/SMB device or read your reviews thoroughly and ensure that you're getting exactly that device (down to the revision number even, sometimes).

    This article clutters the users mind with unnecessary information and technical details which to knowledgeable persons will already be apparent, and recognized as often incorrect; and for the unknowegeable reader - incorrect and irrelevant but taken as true. To rattle off a few
    -switches and hubs, while sharing some features (they're small, blockish and have multiple ports) are also different at an operational level - switches are OSI layer 2 devices, while hubs are electrical devices operating at OSI layer 1.
    -Packets do not get where they need to go because of MAC addresses; frames get where they need to go thanks to MAC addresses while packets are at OSI layer 3 and utilize IP addresses for routing.
    -If you want to see your MAC address via ipconfig, use ipconfig/all. ipconfig on its own will not provide you with this information.

    If I wanted to take a closer read or go through it again, I'm sure I could pull out atleast as many errors as I listed above, but I've gotten enough of my steam out about someone publishing yet more outdated and erroneous technical info or advice in the realm of networking and IT. Please, if you're going to write a tech article, do it with a purpose, stay true to it, make sure you have your stuff down pat, and damn well update it if you're going to re-publish it.

    No one cares about coaxial ethernet anymore, unless you're over the hill or working in some industrial environment with networked machinery, in which case I hope you're not getting your expertise from this article.

    PS. I'd still like to say thanks to Tom's Hardware and that they're an invaluable resource - not just for their reviews and articles, but for the user community they have generated as well. But with that said - is it just me, or is Tom's IT site just one big stream of advertisements in the guise of articles, news stories, and white papers?
  • 0 Hide
    Anonymous , August 8, 2012 4:38 AM
    why are you using blue and brown wires even though they are of no use?