H3C Technologies H3C SecPath F1000-E - Manual (Page 19)

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Reference port
When setting the aggregation state of the ports in an aggregation group, the system automatically picks
a member port as the reference port. A Selected port must have the same port attributes and class-two
configurations as the reference port.
LACP
The IEEE 802.3ad Link Aggregation Control Protocol (LACP) enables dynamic aggregation of physical
links. It uses link aggregation control protocol data units (LACPDUs) for exchanging aggregation
information between LACP-enabled devices.
1. LACP functions
The IEEE 802.3ad LACP offers basic LACP functions and extended LACP functions, as described in Table
2 .
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 aggregation priority, port number, and operational key.
Each member port in a LACP-enabled aggregation group exchanges the above
information with its peer. When a member port receives an LACPDU, it compares
the received information with the information received on the other member ports. In
this way the two systems reach an agreement on which ports should be placed in the
Selected state.
Extended LACP
functions
Implemented by extending the LACPDU with new Type/Length/Value (TLV) fields.
This is how the LACP multi-active detection (MAD) mechanism of the Intelligent
Resilient Framework (IRF) feature is implemented.
• If a device supports both LACP extensions and IRF, it can participate in LACP
MAD either as an IRF member device or an intermediate device.
• If a device supports LACP extensions but not IRF, it can participate in LACP MAD
only as an intermediate device.
2. LACP priorities
There are two types of LACP priorities: system LACP priority and port aggregation priority, as described
in
Table 3 .
Table 3 LACP priorities
Type Description Remarks
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 first and then
the system that has lower priority sets port state accordingly.
Port aggregation
priority Determines the likelihood of a member port to be selected on a system.
The higher port aggregation priority, the higher likelihood.
The smaller the
priority value,
the higher the
priority.