ZyXEL Communications MES3500 Series, User Manual

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MES3500 Series User’s Guide
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H A P T E R
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Link Aggregation
This chapter shows you how to logically aggregate physical links to form one logical, higher-
bandwidth link.
17.1 Link Aggregation Overview
Link aggregation (trunking) is the grouping of physical ports into one logical higher-capacity link.
You may want to trunk ports if for example, it is cheaper to use multiple lower-speed links than to
under-utilize a high-speed, but more costly, single-port link.
However, the more ports you aggregate then the fewer available ports you have. A trunk group is
one logical link containing multiple ports.
The beginning port of each trunk group must be physically connected to form a trunk group.
The Switch supports both static and dynamic link aggregation.
Note: In a properly planned network, it is recommended to implement static link
aggregation only. This ensures increased network stability and control over the
trunk groups on your Switch.
See Section 17.6 on page 150 for a static port trunking example.
17.2 Dynamic Link Aggregation
The Switch adheres to the IEEE 802.3ad standard for static and dynamic (LACP) port trunking.
The Switch supports the link aggregation IEEE802.3ad standard. This standard describes the Link
Aggregation Control Protocol (LACP), which is a protocol that dynamically creates and manages
trunk groups.
When you enable LACP link aggregation on a port, the port can automatically negotiate with the
ports at the remote end of a link to establish trunk groups. LACP also allows port redundancy, that
is, if an operational port fails, then one of the “standby” ports become operational without user
intervention. Please note that:
• You must connect all ports point-to-point to the same Ethernet switch and configure the ports for
LACP trunking.
• LACP only works on full-duplex links.
• All ports in the same trunk group must have the same media type, speed, duplex mode and flow
control settings.