H3C Technologies H3C S12500-X Series Switches - Manual (Page 50)

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LACP functions
LACP offers basic LACP functions and extended LACP functions, as described in Table 3 .
Table 3 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. it 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 priorities
LACP priorities include system LACP priority and port priority, as described in Table 4 . The smaller the
priority value, the higher the priority.
Table 4 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, after which the system that has lower priority
sets port state accordingly.
Port priority
Determines the likelihood of a member port to be selected on a system. The higher port
priority, the higher the likelihood of selection.
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 fails to receive LACPDUs from the peer within the LACP timeout interval, the
member port assumes that the peer port has failed.
The LACP timeout interval also determines the LACPDU sending rate of the peer. You can configure the
LACP timeout interval as the short timeout interval (3 seconds) or the long timeout interval (90 seconds).
If you configure the short timeout interval, the peer sends LACPDUs fast (one LACPDU per second); if you
configure the long timeout interval, the peer sends LACPDUs slowly (one LACPDU every 30 seconds).
How dynamic link aggregation works
The dynamic link aggregation process comprises:
• Choosing a reference port
• Setting the aggregation state of each member port
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.