H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 45)

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in the section Aggregating links in static mode or Choosing a reference port in the section Aggregating
links in dynamic mode .
Link aggregation modes
Link aggregation has the following modes: dynamic and static. Dynamic link aggregation uses Link
Aggregation Control Protocol (LACP) and static link aggregation does not. Table 3 compares the two
aggregation modes.
Table 3 A comparison between static and dynamic aggregation modes
Aggregation
mode
LACP status on
member ports
Pros Cons
Static Disabled
Aggregation is stable. Peers do
not affect the aggregation state of
the member ports.
The member ports do not adjust
the aggregation state according
to that of the peer ports. The
administrator must manually
maintain link aggregations.
Dynamic Enabled
The peer systems maintain the
aggregation state of the member
ports automatically.
Aggregation is unstable. The
aggregation state of the member
ports is susceptible to network
changes.
The following points apply to a dynamic link aggregation group:
• A Selected port can receive and send link aggregation control protocol data units (LACPDUs).
• An Unselected port can receive and send LACPDUs only if it is up and has the same class-two
configurations as the aggregate interface.
LACP
The IEEE 802.3ad LACP enables dynamic aggregation of physical links. It uses link aggregation control
protocol data units (LACPDUs) for exchanging aggregation information between LACP-enabled devices.
• LACP functions
The IEEE 802.3ad LACP offers basic LACP functions and extended LACP functions, as described
in
Table 4 .
Table 4 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
preceding 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 Selected state.
Extended LACP
functions
Implemented by extending the LACPDU with new TLV fields.
• LACP priorities
LACP priorities have the following types: system LACP priority and port aggregation priority.