How dynamic link aggregation works
Choosing a reference port
The system chooses a reference port from the member ports that are in up state and have the same attribute configurations as the aggregate interface. A Selected port must have the same operational key and attribute configurations as the reference port.
The local system (the actor) and the remote system (the partner) negotiate a reference port by using the following workflow:
The two systems compare their system IDs to determine the system with the smaller system ID.
A system ID contains the system LACP priority and the system MAC address.
The two systems compare their LACP priority values.
The lower the LACP priority, the smaller the system ID. If LACP priority values are the same, the two systems proceed to step b.
The two systems compare their MAC addresses.
The lower the MAC address, the smaller the system ID.
The system with the smaller system ID chooses the port with the smallest port ID as the reference port.
A port ID contains a port priority and a port number. The lower the port priority, the smaller the port ID.
The system chooses the port with the lowest priority value as the reference port.
If ports have the same priority, the system proceeds to step b.
The system compares their port numbers.
The smaller the port number, the smaller the port ID.
The port with the smallest port number and the same attribute configurations as the aggregate interface is chosen as the reference port.
Setting the aggregation state of each member port
After the reference port is chosen, the system with the smaller system ID sets the state of each member port on its side.
Figure 10: Setting the state of a member port in a dynamic aggregation group
Meanwhile, the system with the higher system ID is aware of the aggregation state changes on the remote system. The system sets the aggregation state of local member ports the same as their peer ports.
When you aggregate interfaces in dynamic mode, follow these guidelines:
A dynamic link aggregation group preferably sets full-duplex ports as the Selected ports. The group will set only one half-duplex port as a Selected port when either of the following conditions exist:
None of the full-duplex ports can be chosen as Selected ports.
Only half-duplex ports exist in the group.
To ensure stable aggregation and service continuity, do not change the operational key or attribute configurations on any member port.
When the aggregation state of a local port changes in a dynamic aggregation group, the aggregation state of the peer port also changes.
After the Selected port limit is reached, a newly joining port becomes a Selected port if it is more eligible than a current Selected port.
For more information about configuring the maximum number of Selected ports in a dynamic aggregation group, see "Setting the minimum and maximum numbers of Selected ports for an aggregation group."