Figure 10: Stack Of Three Switches With A Linear Trunk - Allied Telesis AT-SB*908 GEN2 Installation Manual

AT-SBx908 GEN2 Installation Guide for Virtual Chassis Stacking
 You can omit the link from the last to first switches to create a
linear trunk. An example of a stack with three switches in a linear
trunk is shown in Figure 10. This trunk topology is not
recommended.
Figure 10. Stack of Three Switches with a Linear Trunk
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