Allied Telesis AT-8100 Series - Manual (Page 514)

Chapter 31: Group Link Control
514
Figure 108. Group Link Control Example 2
With group link control you can address this problem by creating on switch
3 a group of the two ports that connect to switch 1 and the server. Thus,
any change to the link state of the port connected to switch 1 is
automatically transferred to the port connected to the server.
Assume that switch 3 is connected to switch 1 with port 17 and to the
server with port 24, as shown in Figure 109 on page 515. If you group the
two ports with group link control such that port 17 is the upstream or
control port of the group and port 24 is the downstream port, a loss of the
link on port 17 causes the switch to disable port 24, dropping the
connection to the server. The server, having lost connectivity to switch 3,
responds by activating its alternate network interface and transferring the
traffic to switch 4.