Broadcom NetXtreme BCM57 Series, User Manual

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Broadcom Gigabit Ethernet Teaming Services NetXtreme User Guide
Broadcom
®
April 2017 • 2CS57XX-CDUM514-R Page 108
Link Aggregation (IEEE 802.3ad LACP)
Link Aggregation is similar to Generic Trunking except that it uses the Link Aggregation Control Protocol to
negotiate the ports that will make up the team. LACP must be enabled at both ends of the link for the team to
be operational. If LACP is not available at both ends of the link, 802.3ad provides a manual aggregation that
only requires both ends of the link to be in a link up state. Because manual aggregation provides for the
activation of a member link without performing the LACP message exchanges, it should not be considered as
reliable and robust as an LACP negotiated link. LACP automatically determines which member links can be
aggregated and then aggregates them. It provides for the controlled addition and removal of physical links for
the link aggregation so that no frames are lost or duplicated. The removal of aggregate link members is provided
by the marker protocol that can be optionally enabled for Link Aggregation Control Protocol (LACP) enabled
aggregate links.
The Link Aggregation group advertises a single MAC address for all the ports in the trunk. The MAC address of
the Aggregator can be the MAC addresses of one of the MACs that make up the group. LACP and marker
protocols use a multicast destination address.
The Link Aggregation control function determines which links may be aggregated and then binds the ports to an
Aggregator function in the system and monitors conditions to determine if a change in the aggregation group is
required. Link aggregation combines the individual capacity of multiple links to form a high performance virtual
link. The failure or replacement of a link in an LACP trunk will not cause loss of connectivity. The traffic will simply
be failed over to the remaining links in the trunk.