Allied Telesis AT-MC303 - Manual (Page 16)

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With auto-negotiation activated on the media converter, the unit will
determine that the hub is capable of half-duplex only, and will set the port
connected to the hub accordingly. In auto-negotiating with the switch, the
media converter will determine that the device is capable of full-duplex, and
will set the port connected to the switch to full-duplex. The result is referred to
as a classic duplex mode mismatch, where the end nodes are using different
duplex modes.
Figure 3 Duplex Mode Mismatch
There are two options to resolving this problem. One option is to manually
configure the port on the switch that is connected to the media converter so
that it operates only in half-duplex. The second option is to disable auto-
negotiation on the media converter using the A/N button. With auto-
negotiation disabled on the media converter, the switch will assume that the
media converter is capable of only half-duplex mode operation, and will set its
port accordingly, eliminating the mismatch in duplex modes between the end
nodes.
Note
Changing the A/N button setting requires that you power OFF and
power ON the media converter to activate the change on the unit.
100Base switch that
can auto-negotiate the
duplex mode. Ethernet hub capable of
half-duplex mode only.
AT-MC301 Media Converter
STATUS PORT ACTIVITY
100 m
2 km
RS-232 TERMINAL POR T STATUS PORT ACTIVITY 10BASE-T / 10 0BASE-TX 10BASE-T / 10 0BASE-TX FAST ETHERNET SWITCH