Can I visually check that my CAT 5 ethernet cables are correctly wired?

Yes. Here is a description of the color coding of a CAT 5 cable:
========================================== 10/100 BaseT cable - Standard & Crossover ==========================================

Here is the pinout for an RJ45 Ethernet port.

Ethernet Cable colors:
The pairs used in Ethernet are always Orange-Stripe/Orange and
Green-Stripe/Green. This is important because the number of "Twists" in
the wires is different for different pairs.

The twisted pair wire colors on CAT 5 cable are:

Orange-Stripe /Orange
Green-Stripe /Green
Blue-Stripe /Blue
Brown-Stripe /Brown

Here are the pinouts for a "straight-through" Ethernet cable:

Wire                 RJ45              RJ45    Wire
Color                Pin#               Pin#     Color
==================================================
Orange-Stripe  1---------------1         Orange-Stripe
Orange               2---------------2         Orange
Green-Stripe     3---------------3          Green-Stripe
Blue                     4---------------4          Blue
Blue-Stripe        5---------------5          Blue-Stripe
Green                  6---------------6          Green
Brown-Stripe    7---------------7          Brown-Stripe
Brown                 8---------------8          Brown

Here are the pinouts for a "cross-over" Ethernet cable:

Wire RJ45 *                         *RJ45      Wire
Color Pin# *                        *Pin#        Color
==================================================
Orange-Stripe 1---------------3          Orange-Stripe
Orange              2---------------6          Orange
Green-Stripe    3---------------1          Green-Stripe
Blue                    4---------------4          Blue
Blue-Stripe       5---------------5          Blue-Stripe
Green                 6---------------2          Green
Brown-Stripe   7---------------7          Brown-Stripe
Brown                8---------------8          Brown

Another cross-over example in a different format
Wire one side of your cable this way:

Wire color              RJ45 Pin#
--------------------------------------
Orange-Stripe           1  
Orange                        2
Green-Stripe              3
Blue                              4
Blue-Stripe                 5
Green                           6
Brown-Stripe             7
Brown                          8

Wire the OTHER side of the same cable this way:

Wire color        RJ45 Pin#
-----------------------------------------
Green- Stripe             1
Green                           2
Orange-Stripe           3
Blue                              4
Blue-Stripe                 5
Orange                        6
Brown-Stripe             7
Brown                          8

====================================================================

[Originally Published On: 11/11/1999 04:54 PM]