Configuring Link Aggregation - Cisco 200 Series Administration Manual

Port Management

Configuring Link Aggregation

Configuring Link Aggregation
Cisco Small Business 200 Series Smart Switch Administration Guide
Link Aggregation Control Protocol (LACP) is part of an IEEE specification (802.3ad)
that allows you to bundle several physical ports together to form a single logical
channel. Link aggregation optimizes port usage by linking multiple ports together
to form a Link Aggregation Group (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 (Link Aggregation Control Protocol) is
disabled. You configure a static LAG with a group of ports that are always
active members of the LAG.
• Dynamic—A LAG is dynamic if it is LACP-enabled. You define a group of
ports as candidate ports of a dynamic LAG. The LACP determines which
candidate ports from the LAG are active member ports. The non-active
member 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.
This traffic balancing is managed by a hash-based distribution function that
distributes Unicast and Multicast traffic based on packet header information.
The switch support 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
Active member ports in a LAG are defined statically by explicit user assignment or
are dynamically selected by the Link Aggregation Control Protocol (LACP). The
LACP selection process selects the active member ports for the LAG after
exchanging LACP information between the local and remote devices.
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.
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