3Com Switch 4800G 24-Port Configuration Manual page 163

Manual Link Overview
Aggregation
Manual aggregations are created manually. Member ports in a manual
aggregation are LACP-disabled.
Port states in a manual aggregation
In a manual aggregation group, ports are either selected or unselected. Selected
ports can receive and transmit data frames whereas unselected ones cannot.
When setting the state of ports in a manual aggregation group, the system
considers the following:
The system selects the port with the highest priority in the up state as the
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reference port of the aggregation group. Port priority descends in the following
order: full duplex/high speed, full duplex/low speed, half duplex/high speed,
and half duplex/low speed. If multiple ports are of the same priority, the one
with the lowest port number is the reference port.
Ports in the up state with the same speed, duplex mode, link state, and basic
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configuration as the reference port become the candidates for selected ports,
while the other ports become unselected ports.
There is a limit on the number of selected ports in a manual aggregation group.
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If the number of selected-port candidates does not reach the limit, all the
candidates become selected ports; if the number of candidates exceeds the
limit, the candidates with lower port numbers become selected ports, while the
other candidates become unselected ports.
The selected port with the lowest port number serves as the master port of the
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aggregation group, and the other ports serve as the member ports of the
aggregation group.
If all the ports of an aggregations port are down, the port with the lowest port
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number is the master port. In this case, all of them are unselected ports.
In addition, unless the master port should be selected, a port that joins the group
after the limit is reached will not be placed in selected state even if it should be in
normal cases. This is to prevent the ongoing service on selected ports from being
interrupted. You need to avoid the situation however as the selected/unselected
state of a port may become different after a reboot.
Port Configuration Considerations in manual aggregation
As mentioned above, in a manual aggregation group, only ports with
configurations consistent with those of the reference port can become selected.
These configurations include port rate, duplex mode, link state, and other basic
configurations, as described in "Consistency Considerations for Ports in an
Aggregation" on page 161.
You need to maintain the basic configurations of these ports manually to ensure
consistency. As one configuration change may involve multiple ports, this can
become troublesome if you need to do that port by port. As a solution, you may
add the ports into an aggregation port group where you can make configuration
for all member ports.
Approaches to Link Aggregation 163