# 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.

(To network interface card 1).
(To network interface card 2).

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.

Note 4: The pinout of this cable differs from what people usually calls a crossover cable since all pairs are swapped. If you need a crossover cable for use with special applications like serial cables you should not cross the pairs 4/5 and 7/8.

Contributor: | Joakim Ögren, Niklas Edmundsson, Jim C?, Jason D. Pero, Oscar Fernandez Sierra, Cayce Balara, Jeffrey R. Broido, Patrick Smart, Jeffrey R. Broido, Kim Scholte

Source: | IEEE Std 802.3, 2000 Edition

Copyright © The Hardware Book Team 1996-2004.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2004-04-12