Allied Telesis AT-S63 - Manual (Page 192)

Chapter 16: Group Link Control
192 Section II: Advanced Operations
Figure 20. Group Link Control Example 3
When a link on an upstream port is reestablished, the switch automatically
reactivates the downstream counterpart. Referring to the example, when
the link on port 17 is reestablished, the switch enables port 24 again.
A link control group can have more than one upstream and downstream
port. This enables it to support static port trunks and LACP trunks. When a
group has two or more upstream ports, all of the upstream ports must lose
connectivity before the switch disables the downstream ports. This is
illustrated in Figure 21 where a link control group on switch 3 has two
upstream ports, ports 17 and 20, and two downstream ports, port 24 and
25. If connectivity is lost on just port 17, the downstream ports are not
disabled.
Switch 1
Network
Switch 3
Switch 2
Switch 4
Upstream port 17
Downstream port 24