3Com 2928 User Guide - Page 239

The rate of an aggregate interface is the sum of the selected member ports' rates. The duplex mode of an aggregate interface is consistent with that of the selected member ports. Note that all selected member ports use the same duplex mode. For how the state of a member port is determined, refer to Static aggregation mode and Dynamic aggregation mode. LACP protocol The Link Aggregation Control Protocol (LACP) is defined in IEEE 802.3ad. It uses link aggregation control protocol data units (LACPDUs) for information exchange between LACP-enabled devices. LACP is automatically enabled on interfaces in a dynamic aggregation group. For information about dynamic aggregation groups, refer to Dynamic aggregation mode. An LACP-enabled interface sends LACPDUs to notify the remote system (the partner) of its system LACP priority, system MAC address, LACP port priority, port number, and operational key. Upon receiving an LACPDU, the partner compares the received information with the information received on other interfaces to determine the interfaces that can operate as selected interfaces. This allows the two systems to reach an agreement on which link aggregation member ports should be placed in selected state. Operational key When aggregating ports, link aggregation control automatically assigns each port an operational key based on port attributes, including the port rate, duplex mode and link state configuration. In an aggregation group, all selected ports are assigned the same operational key. Class-two configurations The contents of class-two configurations are listed in Table 1-1. In an aggregation group, a member port different from the aggregate interface in the class-two configurations cannot be a selected port. Table 1-1 Class-two configurations Type Considerations Port isolation VLAN Whether a port has joined an isolation group Permitted VLAN IDs, default VLAN, link type (trunk, hybrid, or access), ,tag mode z Some configurations are called class-one configurations. Such configurations, for example, MSTP, can be configured on aggregate interfaces and member ports but are not considered during operational key calculation. For details of MSTP configuration on member ports of link aggregation groups or aggregate interfaces, see related sections in MSTP Configuration. z The change of a class-two configuration setting may affect the select state of link aggregation member ports and thus the ongoing service. To prevent unconsidered change, a message warning of the hazard will be displayed when you attempt to change a class-two setting, upon which you can decide whether to continue your change operation. For details of port isolation configuration and VLAN configuration on member ports of link aggregation groups or aggregate interfaces, see related sections in Port Isolation Configuration and VLAN Configuration. 1-2