Cisco 500 series Administration Manual page 150

Port Management
Configuring Link Aggregation
Cisco 500 Series Stackable Managed Switch Administration Guide
Link Aggregation Overview
Link Aggregation Control Protocol (LACP) is part of the IEEE specification (802.3az)
that enables you to bundle several physical ports together to form a single logical
channel (LAG). LAGs multiply the bandwidth, increase port flexibility, and provide
link redundancy between two devices.
Two types of LAGs are supported:
• Static—A LAG is static if the LACP is disabled on it. The group of ports
assigned to a static LAG are always active members. After a LAG is manually
created, the LACP option cannot be added or removed, until the LAG is
edited and a member is removed (which can be added prior to applying),
then the LACP button become available for editing.
• Dynamic—A LAG is dynamic if LACP is enabled on it. The group of ports
assigned to dynamic LAG are candidate ports. LACP determines which
candidate ports are active member ports. The non-active candidate ports
are standby ports ready to replace any failing active member ports.
Load Balancing
Traffic forwarded to a LAG is load-balanced across the active member ports, thus
achieving an effective bandwidth close to the aggregate bandwidth of all the
active member ports of the LAG.
Traffic load balancing over the active member ports of a LAG is managed by a
hash-based distribution function that distributes Unicast and Multicast traffic
based on Layer 2 or Layer 3 packet header information.
The switch supports two modes of load balancing:
• By MAC Addresses—Based on the destination and source MAC addresses
of all packets.
• By IP and MAC Addresses—Based on the destination and source IP
addresses for IP packets, and destination and source MAC addresses for
non-IP packets.
LAG Management
In general, a LAG is treated by the system as a single logical port. In particular, the
LAG has port attributes similar to a regular port, such as state and speed.
The switch supports eight LAGs.
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