Allied Telesis AT-FS705PD - Manual (Page 14)

Overview
6
Auto MDI/MDI-X
A 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. A twisted pair
port on a PC, router, or bridge is typically wired as MDI, while a twisted pair
port on a switch or hub is usually MDI-X.
To connect two 10 Mbps or 100 Mbps network devices together that have
dissimilar port wiring configurations, such as an MDI to MDI-X, you would
use a straight-through twisted pair cable. To connect two networks devices
that have the same wiring configuration, such as MDI to MDI, you would use
a crossover cable.
The AT-FS705PD switch features automatic MDI/MDI-X. The twisted pair
port automatically determines the configurations of the port on the device to
which it is connected and then configures itself appropriately. For example, if
a port on a switch is connected to a port on a bridge, which is typically wired
as MDI, the port on the switch automatically configures itself as MDI-X. This
feature allows you to use either a crossover cable or a straight-through cable
when connecting a device to a twisted pair port.
MAC Address Table
The heart of an Ethernet switch is the Media Access Control (MAC) address
table. Every device that you attach to an Ethernet network has a MAC
address. This address is assigned to the device by the device’s manufacturer.
For example, each Network Interface Card (NIC) that you install into your
network computers has a MAC address that was assigned to it by the card’s
manufacturer.
A switch’s MAC address table is a list of the MAC addresses of the devices
that are connected to its ports. The switch uses this table to direct data frames
to their appropriate destination end-nodes, and in some cases, to discard
frames that it receives. The switch creates the MAC address table by
examining the frames that it receives on its ports. Each frame is examined for
its source address; that is, the MAC address of the end-node that sent the
frame. The switch checks to determine whether the address is already in its
MAC address table. If it is not, the switch adds the address to the table along
with the port number on which the frame was received. The result is a table
that contains a list of all the MAC addresses of end-nodes that have sent
frames to the switch and the ports on the switch to which the end-nodes are
connected.