Aggregating links in dynamic mode, Selecting a reference port, Setting the aggregation state of each member port – H3C Technologies H3C S5120 Series Switches User Manual
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Because any port attribute or class-two configuration change on a member port may cause the
aggregation state of the port and other member ports to change and thus affect services, it is
recommended that you do that with caution.
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A port that joins the static aggregation group after the selected port limit has been reached will not
be placed in the selected state even if it should be in normal cases. This is to prevent the ongoing
traffic on the current selected ports from being interrupted. You should avoid the situation however,
as this may cause the aggregation state of a port to change after a reboot.
Aggregating Links in Dynamic Mode
LACP is automatically enabled on all member ports in a dynamic aggregation group. The protocol
maintains the aggregation state of ports automatically.
Dynamic link aggregation comprises:
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Setting the aggregation state of each member port
Selecting a reference port
The local system (the actor) negotiates with the remote system (the partner) to select a reference port
as follows:
1) Compare the system ID (comprising the system LACP priority and the system MAC address) of the
actor with that of the partner. The system with the lower LACP priority value wins out. If they are the
same, compare the system MAC addresses. The system with the lower MAC address wins out.
2) Compare the port IDs of the ports on the system with the smaller system ID. A port ID comprises a
port LACP priority and a port number. First compare the port LACP priorities. The port with the
lower LACP priority value wins out. If two ports have the same LACP priority, compare their port
numbers. The port with the smaller port number wins out. Thus, the port with the lowest port ID is
selected as the reference port.
Setting the aggregation state of each member port
After the reference port is selected, the system with the lower system ID sets the state of each member
port in the dynamic aggregation group on its side as shown in
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