H3C Technologies H3C S3100 Series Switches - Manual (Page 159)

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z The ports connected to a peer device different from the one the master port is 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.
z The system sets the ports with basic port configuration different from that of the master port to
unselected state.
z There is a limit on the number of selected ports in an aggregation group. 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.
Dynamic LACP Aggregation Group
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. Ports can be aggregated into a dynamic aggregation group only when they
are connected to the same peer device and have the same speed, duplex mode, and basic
configurations, and so are/do their peer ports.
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.
Port status of dynamic aggregation group
A port in a dynamic aggregation group can be in one of the two states: selected and unselected.
z Both the selected and the unselected ports can receive/transmit LACP protocol packets;
z The selected ports can receive/transmit user service packets, but the unselected ports cannot.
z In a dynamic aggregation group, the selected port with the smallest port number serves as the
master port of the group, and other selected ports serve as member ports of the group.
There is a limit on the number of selected ports in an aggregation group. Therefore, if the number of the
member ports that can be set as selected ports in an aggregation group exceeds the maximum number
supported by the device, the system will negotiate with its peer end, to determine the states of the
member ports according to the port IDs of the preferred device (that is, the device with smaller system
ID). The following is the negotiation procedure:
1) Compare device IDs (system priority + system MAC address) between the two parties. First
compare the two system priorities, then the two system MAC addresses if the system priorities are
equal. The device with smaller device ID will be considered as the preferred one.
2) Compare port IDs (port priority + port number) on the preferred device. The comparison between
two port IDs is as follows: First compare the two port priorities, then the two port numbers if the two
port priorities are equal; the port with the smallest port ID is the selected port and the left ports are
unselected ports.
For an aggregation group: