Ethernet 10/100/1000Base-T and 100Base-T4 Crossover
This cable can be used to cascade hubs, or for connecting two Ethernet stations back-to-back without a hub. It works with 10Base-T, 100Base-TX, 100Base-T4 and 1000Base-T. Use a good enough cable, if you are confused about categories of cables then use category 5e(nhanced) and you’ll be fine even at 1000Base-T.
RJ45 MALE CONNECTOR to network interface card 1.
RJ45 MALE CONNECTOR to network interface card 2.
(1000Base-T names in parentheses)
| Name | NIC1 | Color | NIC2 | Name |
|---|---|---|---|---|
| TX+ (BI_DA+) | 1 | White/Orange | 3 | RX+ (BI_DB+) |
| TX- (BI_DA-) | 2 | Orange | 6 | RX- (BI_DB-) |
| RX+ (BI_DB+) | 3 | White/Green | 1 | TX+ (BI_DA+) |
| - (BI_DC+) | 4 | Blue | 7 | - (BI_DD+) |
| - (BI_DC-) | 5 | White/Blue | 8 | - (BI_DD-) |
| RX- (BI_DB-) | 6 | Green | 2 | TX- (BI_DA-) |
| - (BI_DD+) | 7 | White/Brown | 4 | - (BI_DC+) |
| - (BI_DD-) | 8 | Brown | 5 | - (BI_DC-) |
That means that the white/orange cable connected to NIC 1 pin 1 should go to NIC 2 pin 3 and NIC 1 pin 2 to NIC 2 pin 6 etc.
Note 1: It’s important that each pair is kept as a pair. TX+ & TX- must be in the pair, and RX+ & RX- must together in another pair. (Just as the table above shows).
Note 2: While 10Base-T and 100Base-TX only uses 2 pairs, please connect all four since 100Base-T4 and 1000Base-T needs them and save yourself some future debugging 
Note 3: The colors originate from the numbering and name on NIC1.
RJ-45 Connectors – Patch Cables for Category 5 Wire
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REMEMBER
To hold the RJ45 connector with the ‘clip’ on the bottom. To have to the ‘opening’ (where you insert the cable) facing you. |
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| CAT5 Standard Patch Cord | CAT5 Cross-over Cable | |
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REMEMBER
For a cross-over cable make one end like the Standard Patch Cord, and one end like the Cross-over Cable. |
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| Straight-Through vs. Cross-Over
In general, the patch cords that you use with your Ethernet connections are “straight-through”, which means that pin 1 of the plug on one end is connected to pin 1 of the plug on the other end. In this particular case it is not then important to wire them as above. Pin 1 is Pin 1 etc etc. However for the sake of uniformity it may be best to wire your cables with the same colour sequence. Cross-Over cables are “crossed” end to end data cables aren’t. If you have a network hub that has an uplink port on it then you do not need to make (or purchase a cross-over cable). Just switch the port on the hub to the ‘uplink’ mode. If your hub does not have an ‘uplink’ port on it then the only way to cascade another hub or attach a cable modem is to use a cross-over cable. It helps for future reference to mark or attach a tag to the cross-over cable so that you do not attempt to use it as a ‘normal’ patch lead at some time in the future. The only time you cross connections in 10/100BaseT is when you connect two Ethernet devices directly together without a hub. This can be two computers connected without a hub, or two hubs via standard Ethernet ports in the hubs. Then you need a “cross-over” patch cable, which crosses the transmit and receive pairs, the orange and green pairs in normal wiring. In a cross-over cable, one end is normal, and the other end has the cross-over configuration. Remember you can only network two computers together with Cat5 cable. To add extra PC’s to your network you will require a hub. |
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