15 LINK AGGREGATION OVERVIEWn Link aggregation is not supported on MSR 20 series routers. It is only supported oninterfaces of 16FSW/24FSW modules of MSR 30/MSR 50 series routers.Link aggregation aggregates multiple physical Ethernet ports into one logical link,also called a logical group, to increase reliability and bandwidth.This chapter covers these topics:■ “Link Aggregation Overview” on page 345■ “LACP” on page 345■ “Load Sharing in a Link Aggregation Group” on page 349■ “Aggregation Port Group” on page 349Link Aggregation Link aggregation allows you to increase bandwidth by distributingincoming/outgoing traffic on the member ports in an aggregation group. Inaddition, it provides reliable connectivity because these member ports candynamically back up each other.This section covers these topics:■ “LACP” on page 345■ “Consistency Considerations for Ports in an Aggregation” on page 346LACP The link aggregation control protocol (LACP), as defined in IEEE 802.3ad, is usedfor link aggregation control.LACP interacts with its peer by sending link aggregation control protocol dataunits (LACPDUs).By adding a port to a static aggregation group, you can enable LACP on the port.After LACP is enabled on a port, the port sends an LACPDU to notify the remotesystem of its system LACP priority, system MAC address, port LACP priority, portnumber, and operational key. Upon receipt of an LACPDU, the remote systemcompares the received information with the information received on other ports todetermine the ports that can operate as selected ports. This allows the twosystems to reach an agreement on whether a port is a selected port.When aggregating ports, link aggregation control automatically assigns each portan operational key based on its rate, duplex mode, and other basic configurations.In an aggregation group, the selected ports share the same operational key.
