Allied Telesis AT-FS202SC/FS1 - Manual (Page 20)

Chapter 1: Overview
10
Auto MDI/MDI-X
An RJ-45 twisted pair port on a 10 Mbps or 100 Mbps Ethernet network
device can have one of two possible wiring configurations: MDI or MDI-X.
The RJ-45 port on a PC, router, or bridge is typically wired as MDI, while
the twisted pair port on a converter or hub is usually MDI-X.
When the twisted pair port on the AT-FS201, AT-FS202, and
AT-FS202SC/FS1 converters is set to Auto-Negotiation, the port features
automatic MDI/MDI-X. The RJ-45 port automatically determines the
configuration of the port on the end-node and then configures itself
appropriately. This feature allows you to use either a straight-through or
crossover cable when connecting an end-node to the twisted pair port.
When the port on the AT-FS201, AT-FS202, and AT-FS202SC/FS1
converter is not set to Auto-Negotiation, the port defaults to MDI-X. To
connect to an end-node that has the same wiring configuration, such as
MDI-X to MDI-X, you would use a crossover twisted pair cable. To
connect to an end-node that has different port wiring configuration, such
as MDI to MDI-X, you would use a straight-through cable.