Allied Telesis AR700 SERIES Software Release 2.7.1 - Manual (Page 68)

68 AR700 Series Router User Guide
Software Release 2.7.1
C613-02047-00 REV A
Port Speed and Duplex Mode
Switch ports can operate at either 10 Mbps or 100 Mbps, in either full duplex or
half duplex mode. In full duplex mode a port can transmit and receive data
simultaneously. In half duplex mode a port can either transmit or receive data,
but not at the same time. This versatility makes it possible to connect devices
with different speeds and duplex modes to different switch ports. Such
versatility also requires that each switch port knows which speed and mode to
use.
Each switch port can be either configured with a fixed speed and duplex mode,
or configured to autonegotiate speed and duplex mode with a device
connected to it to determine a speed and mode that will allow successful
transmission. Setting the switch port to a fixed speed and duplex mode allows
the port to support equipment that cannot autonegotiate. Autonegotiation
allows the switch ports to adjust their speed and duplex mode to accommodate
the devices connected to them. An autonegotiating switch port will adopt the
speed and duplex mode required by devices connected to it. If another
autonegotiating device is connected to the switch port, they will negotiate the
highest possible common speed and duplex mode. When a port at one end of
the link is set to a fixed speed (non-autonegotiating) set the port at the other
end of the link to operate at the same speed. This is because when
autonegotiation is disabled, the link partner is not able to determine the duplex
mode of the link and must be forced to use the correct mode.
It is also possible to require a switch port to operate at a single speed without
disabling autonegotiation by allowing the port to autonegotiate, but constrain
the speed/duplex options to the desired combination. For example, if one end
of a link is set to AUTO and other to 100MFULL then the AUTO end will select
100MHALF operation because without the other end autonegotiating the
AUTO end has no way of knowing that the fixed end is full duplex capable. If a
particular speed is required it is usually preferable to fix the speed/duplex
combination using one of the autonegotiating speed values. Therefore, using
100MFAUTO at one end of a link and will allow the AUTO end to
autonegotiate 100MFULL.
To change this setting use the command:
set switch port={port-list|all}
speed={autonegotiate|10mhalf|10mfull|10mhauto|10mfauto|
100mhalf|100mfull|100mhauto|100mfauto} [other-options...]
The SPEED parameter specifies the configured line speed and duplex mode of
the port(s). If AUTONEGOTIATE is specified, the port(s) will autonegotiate the
highest mutually possible line speed and duplex mode with the link partner. If
one of 10MFAUTO, 10MHAUTO, 100MFAUTO, or 100MHAUTO is specified,
the port will autonegotiate with the link partner, but only accept operation at
the specified speed and duplex mode. If one of 10MHALF, 10MFULL,
100MHALF, or 100MFULL is specified, then autonegotiation is disabled and
the interface is forced to operate at the specified speed and duplex mode,
regardless of whether the link partner is capable of working at that speed. The
default is AUTONEGOTIATE.