I don't even want to get into the "RJ-45" Connector naming issue, but I guess I will. Ethernet does not use a RJ-45 connector. Ethernet uses a 8P8C connector. a RJ-45 is a mechanically-keyed variation of the 8P8C body with an extra tab that prevents it from mating with other connectors, used in telecom applications.
Hope this sheds some light on issues you never knew were an issue, LOL