Figure 19: Cabling 10Gbps Ports As A Stack Trunk - Allied Telesis AT-x550-18XTQ Installation Manual

Chapter 2: Virtual Chassis Stacking
Stack of Two Switches
Stack of Three Switches
62
 As with 40Gbps trunks, the stack cables of 10Gbps trunks must
cross over to different stack ports on the switches. For example,
when cabling two AT-x550-18XSQ Switches, the connection of the
transceiver in slot 17 has to connect to the transceiver in slot 18 in
the next switch. Figure 19 shows the correct wiring configurations
for stacks of two, three, or four switches.
Caution
The switches will not form the stack if the connections do not cross
over, but will instead operate as stand-alone devices.  E78
Figure 19. Cabling 10Gbps Ports as a Stack Trunk
Stack of Four Switches