3Com 2928 User Guide - Page 240

Link Aggregation Modes Depending on the link aggregation procedure, link aggregation operates in one of the following two modes: z Static aggregation mode z Dynamic aggregation mode Static aggregation mode LACP is disabled on the member ports in a static aggregation group. In a static aggregation group, the system sets a port to selected or unselected state by the following rules: z Select a port as the reference port from the ports that are in up state and with the same class-two configurations as the corresponding aggregate interface. These ports are selected in the order of full duplex/high speed, full duplex/low speed, half duplex/high speed, and half duplex/low speed, with full duplex/high speed being the most preferred. If two ports with the same duplex mode/speed pair are present, the one with the lower port number wins out. z Consider the ports in up state with the same port attributes and class-two configurations as the reference port as candidate selected ports, and set all others in the unselected state. z Static aggregation limits the number of selected ports in an aggregation group. When the number of the candidate selected ports is under the limit, all the candidate selected ports become selected ports. When the limit is exceeded, set the candidate selected ports with smaller port numbers in the selected state and those with greater port numbers in the unselected state. z If all the member ports are down, set their states to unselected. z Set the ports that cannot aggregate with the reference port to the unselected state. A port that joins the aggregation group after the limit on the number of selected ports has been reached will not be placed in the selected state even if it should be in normal cases. This can prevent the ongoing traffic on the current selected ports from being interrupted. You should avoid the situation however, as this may cause the selected/unselected state of a port to change after a reboot. Dynamic aggregation mode LACP is enabled on member ports in a dynamic aggregation group. In a dynamic aggregation group, z A selected port can receive and transmit LACPDUs. z An unselected port can receive and send LACPDUs only if it is up and with the same configurations as those on the aggregate interface. In a dynamic aggregation group, the system sets the ports to selected or unselected state in the following steps: 1) The local system (the actor) negotiates with the remote system (the partner) to determine port state based on the port IDs on the end with the preferred system ID. The following is the detailed negotiation procedure: 1-3