Table 49. Link Control Groups On Switch 3 In Example 6 - Allied Telesis AT-8100L/8 User Manual

approach is to create groups in which the ports are connected to the same
network node. This is useful in network topologies where redundant static
port trunks or LACP trunks are controlled by the spanning tree protocol. If
a primary trunk loses bandwidth capacity because connectivity is lost on
one or more of the links and there is a redundant trunk held in the blocking
state by the spanning tree protocol, it may be advantageous to shut down
an impaired trunk and activate a redundant trunk, to restore full bandwidth.
This is illustrated in this figure. Switch 1 and switch 3 are connected with a
static or LACP trunk of three links. A backup trunk from switch 2 to switch
3 is placed in the blocking state by the spanning tree protocol to prevent a
network loop.
Figure 112. Group Link Control Example 6
Let's assume you want switch 3 to shut down the primary trunk to switch 1
if the active trunk loses one link. For this, you would create a series of
groups to cover all of the possible combinations. Each port is designated
as an uplink port in one group and a downstream port in the other groups.
There are three possible combinations, as shown in this table. The order
of the groups is unimportant.

Table 49. Link Control Groups on Switch 3 in Example 6

Link Control
Upstream Port
Group
1 7
2 8
AT-8100 Switch Command Line User's Guide
Downstream Ports
8, 9
7, 9
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