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Table 2 Basic and extended LACP functions
Category
Description
Basic LACP functions
Implemented through the basic LACPDU fields, including the system LACP
priority, system MAC address, port priority, port number, and operational key.
Extended LACP
functions
Implemented by extending the LACPDU with new TLV fields. This is how the
LACP MAD mechanism of the IRF feature is implemented.
The switch series can participate in LACP MAD as either an IRF member device or
an intermediate device.
For more information about IRF and the LACP MAD mechanism, see
IRF
Configuration Guide
.
LACP operating modes
LACP can operate in active mode or passive mode.
When LACP is operating in passive mode on a local member port and its peer port, both ports cannot
send LACPDUs. When LACP is operating in active mode on the port on either end of a link, both
ports can send LACPDUs.
LACP priorities
LACP priorities include system LACP priority and port priority, as described in
. The smaller
the priority value, the higher the priority.
Table 3 LACP priorities
Type Description
System LACP
priority
Used by two peer devices (or systems) to determine which one is superior in link
aggregation.
In dynamic link aggregation, the system that has higher system LACP priority sets
the Selected state of member ports on its side. The system that has lower priority
sets the aggregation state of local member ports the same as their respective peer
ports.
Port priority
Determines the likelihood of a member port to be selected on a system. A port with a
higher port priority is more likely to become Selected.
LACP timeout interval
The LACP timeout interval specifies how long a member port waits to receive LACPDUs from the
peer port. If a local member port does not receive LACPDUs from the peer within the LACP timeout
interval, the member port considers the peer as failed.
The LACP timeout interval also determines the LACPDU sending rate of the peer. LACP timeout
intervals include the following types:
•
Short timeout interval
—3 seconds. If you use the short timeout interval, the peer sends one
LACPDU per second.
•
Long timeout interval
—90 seconds. If you use the long timeout interval, the peer sends one
LACPDU every 30 seconds.
How dynamic link aggregation works
Choosing a reference port
The system chooses a reference port from the member ports that are in up state and have the same
attribute configurations as the aggregate interface. A Selected port must have the same operational
key and attribute configurations as the reference port.
