Allied Telesis AT-FS970M Series - Manual (Page 496)

Chapter 29: Group Link Control
496
Only one group has to be true for the switch to shut down the ports of the
trunk. If, for instance, port 8 loses connectivity, making group 2 true, the
switch shuts down ports 7 and 9. When connectivity is restored on port 8,
it enables ports 7 and 9 again.
In this example, the primary and backup trunks have four links each.
Figure 108. Group Link Control Example 7
If you want switch 3 to shut down the primary trunk if two links are lost, you
create six groups to cover all of the possible combinations. The groups are
listed in Table 48 on page 497. As mentioned previously, only one of the
groups has to be true for the switch to disable the remaining ports in the
trunk. For instance, a loss of connectivity on ports 8 and 10 makes group 5
true, causing the switch to disable ports 7 and 9, which shuts down the
trunk. If a link is reestablished on either port 8 or 10, the switch activates
ports 7 and 9 again.
3 9 7, 8
Table 47. Link Control Groups on Switch 3 in Example 6
Link Control
Group
Upstream Port Downstream Ports