Allied Telesis SwitchBladex8112 Installation Manual page 235

Section II: Installing the Chassis
SwitchBlade x8112 Chassis Switch and AT-SBx81CFC960 Card Installation Guide
 The default speed setting of Auto-Negotiation is not appropriate for
ports connected to network devices that do not support Auto-
Negotiation and have fixed speeds or 10 or 100 Mbps. For those
switch ports, you should disable Auto-Negotiation and set the
port's speed manually to match the speeds of the network devices.

The ports must be set to Auto-Negotiation, the default setting, to
operate at 1000Mbps.
 The default duplex mode setting for the ports is Auto-Negotiation.
This setting is appropriate for ports connected to network devices
that also support Auto-Negotiation for duplex modes.
 The default duplex mode setting of Auto-Negotiation is not
appropriate for ports connected to network devices that do not
support Auto-Negotiation and have a fixed duplex mode. Disable
Auto-Negotiation on those ports and set the duplex modes
manually to avoid the possibility of duplex mode mismatches. A
switch port using Auto-Negotiation defaults to half-duplex if it
detects that the end node is not using Auto-Negotiation, which can
result in a mismatch if the end node is operating at a fixed duplex
mode of full-duplex.
Note
The AT-SBx81GT40 Line Card does not support half-duplex mode.
Yet another source for a poor or intermittent link can be a MDI/MDIX wiring
configuration mismatch. The wiring configurations of the ports on the AT-
SBx81GT24, AT-SBx81GT40, and AT-SBx81GP24 Line Cards are set
automatically with automatic MDIX detection when the ports are operating
at 10 or 100 Mbps. (Automatic MDIX detection does not apply to the ports
when they are operating at 1000 Mbps.) You may not disable this feature
on the ports. For automatic MDIX detection to work successfully, the
network device connected to a port must also support the feature. If it does
not, a port on the switch defaults to MDIX. This may require the use of a
crossover cable. Here are the guidelines to choosing straight-through or
crossover cables for the ports:

You may use straight-through cables on ports that are connected
to network devices that operate at 1000 Mbps.
 You may use straight-through or crossover cables on ports that are
connected to network devices that support automatic MDIX
detection and that operate at 10 or 100 Mbps.
 You must use straight-through cables on ports that are connected
to network devices that have a fixed wiring configuration of MDI
and that operate at 10 or 100 Mbps.
 You must use crossover cables on ports that are connected to
network devices that have a fixed wiring configuration of MDIX and
that operate at 10 or 100 Mbps.
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