Allied Telesis AT-FS970M Series - Manual (Page 492)

Chapter 29: Group Link Control
492
Figure 103. 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 104 on page 493. 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.