The most common Ethernet RJ45 specification is T568B.

See the T568B picture on the left.

Most network hardware can use the same wiring on both ends without needing crossover wiring. Older systems sometimes needed crossover cables - like when a user wanted to cable from computer to computer. New computers detect and adjust for either wire spec in the cable.

For Ethernet to work, different wiring schemes can be used, but a consistent standard like T568B makes cable maintenance easier.

Cheaper Asian Pre-Terminated Cables

Know that cheap cables terminated in Asia can use different wiring specs. The wires will often come with an RJ45 plug upside down on both ends. This is not a problem for communications, but it is not the standard.

This is an example of a patch cable purchased on Amazon that is backwards to T568B.