Installation guide

Chapter 9: Troubleshooting
152
 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.
The MDI/MDIX wiring configurations of the ports on the AT-SBx81GT24
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
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.