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Chapter 3 General Management of the Switch 3-107
3.4.3 Configuring Aggregated Links
You can create multiple links between devices that work as one virtual, aggregate
link. An aggregated link offers a dramatic increase in bandwidth for network
segments where bottlenecks exist, as well as providing a fault-tolerant link between
two devices. You can create up to six aggregated links at a time.
The switch supports both static aggregated links and dynamic Link Aggregation
Control Protocol (LACP). LACP configured ports will automatically negotiate a link
with LACP-configured ports on another device. You can configure any number of
the up-link ports on the switch as LACP, as long as they are not already configured
as part of a static link. If ports on another device are also configured as LACP, the
switch and the other device will negotiate an aggregated link between them. If an
LACP link consists of more than four ports, all other ports will be placed in a
standby mode. If one link in the aggregated link fails, one of the standby ports will
automatically be activated to replace it.
Besides balancing the load across each port in the aggregated link, the additional
ports provide redundancy by taking over the load if a port in the aggregated link
fails. However, before making any physical connections between devices, use the
web interface or CLI to specify the aggregated link on the devices at both ends.
When using aggregated links, take note of the following points:
■ Finish configuring aggregated links before you connect the corresponding
network cables between switches, to avoid creating a loop.
■ You can create up to six aggregated links on the switch, with up to four ports per
aggregated link.
■ The ports at both ends of a connection must be configured as aggregated links (in
some device interfaces, the word “trunk” might be used to refer to an aggregated
link).
■ The ports at both ends of an aggregated link must be configured in an identical
manner, including communication mode (speed, duplex mode and flow control),
VLAN assignments, and COS settings.
■ If the target switch has also enabled LACP on the connected ports, the aggregated
link will be activated automatically.
■ An aggregated link formed with another switch using LACP will automatically be
assigned the next available port-channel number.
■ If more than four ports attached to the same target switch have LACP enabled,
the additional ports will be placed in standby mode, and will only be enabled if
one of the active links fails.
■ All the ports in an aggregated link have to be treated as a whole when moved
from or to, or when added to or deleted from, a VLAN.
■ STP, VLAN, and IGMP settings can only be made for the entire aggregated link.