ZyXEL Communications ES-2108 User Manual

ES-2108 Series User’s Guide

Chapter 15 Link Aggregation

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This chapter shows you how to logically aggregate physical links to form one logical, higher-
bandwidth link.

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 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 Aggregate 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. 

Configure trunk groups or LACP before you connect the Ethernet switch to avoid causing 
network topology loops.