Feature Overview - Nokia ESB26 User Manual

7.

Feature Overview

Static Link Aggregation Groups (LAGs)
Static LAGs provide the ability to treat multiple switch ports as one switch port. These port
groups act as a single logical port for high-bandwidth connections between two network
devices. A static LAG balances the traffic load across the links in the channel. If a physical
link within the static LAG fails, traffic previously carried over the failed link is moved to the
remaining links. Most protocols operate over either single ports or aggregated switch ports
and do not recognize the physical ports within the port group.
A static LAG consists of individual Fast Ethernet links bundled into a single logical link as
shown in Figure 7-1: "Four Ports Combined into a Link Aggregation Group".
Benefits
Static LAGs provide the following benefits:
• Increased bandwidth
The capacity of multiple interfaces is combined into one logical link. Besides
increasing bandwidth, link aggregation also provides intermediate data rate
levels between the standard data rates of 10 Mbps, 100 Mbps, and 1000 Mbps,
as well as rates beyond 1000 Mbps if required.
• Increased availability
If a link within a LAG fails or is replaced, the traffic is not disrupted and
communication is maintained (even though the available capacity is reduced).
• Load sharing
Traffic is distributed across multiple links, minimizing the probability that a
single link be overwhelmed.
• Use of existing hardware
Software replaces the need to upgrade the hardware to higher bandwidth
capacity.
The Link Aggregation Control Protocol (LACP)
LACP, specified in the IEEE standard 802.3ad, provides a standardized means for
dynamically exchanging information between two switches in order to configure and maintain
link aggregation groups automatically. LACP can automatically detect the presence of other
aggregation-capable network devices in the system. It enables you to determine which links in
a system can be aggregated. For each aggregatable link, the switches exchange LACP frames
in order to allocate the link to a Link Aggregation Group.
LACP Modes
The LACP interface supports two modes of operation, as follows:
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Link Aggregation Groups (LAGs)
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