Allied Telesis AT-S106 - Manual (Page 90)

Chapter 7: LACP Port Trunks
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LACP System Priority
It is possible for two devices interconnected by an aggregate trunk to
encounter a conflict when they form the trunk. For example, the two
devices might not support the same number of active ports in an
aggregate trunk or might not agree on which ports are active and which
are in standby mode.
If a conflict does occur, the two devices need a mechanism for resolving
the problem and deciding whose LACP settings take precedence. This is
the function of the system LACP priority value. A hexadecimal value of
from 1 to FFFF, this value is used whenever the devices encounter a
conflict creating a trunk—the lower the number, the higher the priority. As
a result, the settings on the device with the higher priority take precedence
over the settings on the other device. If both devices have the same
system LACP priority value, the settings on the switch with the lowest
MAC address take precedence. In the AT-S106 Management software,
the MAC address is called the System ID.
The LACP System Priority is pre-assigned and you cannot alter this
parameter.
Key Parameter
The key parameter is a hexadecimal value from 1 to FFFF that identifies
an aggregator. Each aggregator on a switch must have a unique key
parameter value. The key is restricted to a switch. Two aggregators on
different switches can have the same key without generating a conflict.
The switch automatically assigns these keys and you cannot be change
this parameter.
LACP Port Priority Value
The switch uses a port’s LACP priority to determine which ports are active
and which are in the standby mode in situations where the number of ports
in the aggregate trunk exceeds the highest allowed number of active
ports. This parameter is a hexadecimal value in a range of 1 to FFFF,
based on the port number. For instance, the priority values for ports 2 and
11 are 0002 and 000B, respectively. The lower the number, the higher the
priority. Ports with the highest priorities are designated as the active ports
in an aggregate trunk.
For example, if both 802.3ad-compliant devices support up to eight active
ports and there are a total of ten ports in the trunk, the eight ports with the
highest priorities (lowest priority values) are designated as the active