3Com 4210 PWR Configuration Manual page 111

Dynamic LACP
Aggregation Group
must contain at least one port. When a static aggregation group contains only one
port, you cannot remove the port unless you remove the whole aggregation
group.
LACP is enabled on the member ports of static aggregation groups. When you
remove a static aggregation group, all the member ports in up state form one or
multiple dynamic aggregations with LACP enabled. LACP cannot be disabled on
static aggregation ports.
Port status of static aggregation group
A port in a static aggregation group can be in one of the two states: selected or
unselected.
Both the selected and the unselected ports can transceive LACP protocol
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packets.
Only the selected ports can transceive service packets; the unselected ports
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cannot.
In a static aggregation group, the system sets the ports to selected or unselected
state according to the following rules.
Among the ports in an aggregation group that are in up state, the system
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determines the master port with one of the following settings being the
highest (in descending order) as the master port: full duplex/high speed, full
duplex/low speed, half duplex/high speed, half duplex/low speed. The ports
with their rate, duplex mode and link type being the same as that of the master
port are selected port, and the rest are unselected ports.
The ports connected to a peer device different from the one the master port is
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connected to or those connected to the same peer device as the master port
but to a peer port that is not in the same aggregation group as the peer port of
the master port are unselected ports.
The ports unable to aggregate with the master port (due to some hardware
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limit) are unselected ports.
The system sets the ports with basic port configuration different from that of
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the master port to unselected state.
There is a limit on the number of selected ports in an aggregation group.
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Therefore, if the number of the selected ports in an aggregation group exceeds
the maximum number supported by the device, those with lower port numbers
operate as the selected ports, and others as unselected ports.
Introduction to dynamic LACP aggregation group
A dynamic LACP aggregation group is automatically created and removed by the
system. Users cannot add/remove ports to/from it. A port can participate in
dynamic link aggregation only when it is LACP-enabled. Ports can be aggregated
into a dynamic aggregation group only when they are connected to the same peer
device and have the same basic configuration (such as rate and duplex mode).
Besides multiple-port aggregation groups, the system is also able to create
single-port aggregation groups, each of which contains only one port. LACP is
enabled on the member ports of dynamic aggregation groups.
Link Aggregation Classification 109