Allied Telesis x510 Series - Manual (Page 103)

x510 Series Installation Guide for Virtual Chassis Stacking
103
 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. You
should disable Auto-Negotiation on those ports and set their 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.
 Do not attach cables to ports of static or LACP port trunks until
after you have configured the trunks on the switch. Otherwise, the
ports will form network loops that can adversely affect network
performance.