H3C Technologies H3C S5120 Series Switches - Manual (Page 101)

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z Class-two configurations made on an aggregate interface are automatically synchronized to all its
member ports. These configurations are retained on the member ports even after the aggregate
interface is removed.
z Any class-two configuration change may affect the aggregation state of link aggregation member
ports and thus ongoing traffic. To make sure that you are aware of the risk, the system displays a
warning message every time you attempt to change a class-two configuration setting on a member
port.
z Class-one configurations, which are configurations that do not affect the aggregation state of the
member port even if they are different from those on the aggregate interface. MSTP setting is
example of class-one configurations.
Reference port
When setting the aggregation state of the ports in an aggregation group, the system automatically picks
a member port as the reference. This port is called the reference port of the aggregation group. The port
attribute and class-two configurations of every other member port are compared with those of the
reference port.
LACP protocol
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
Based on the fields carried in LACPDUs, the functions delivered by the IEEE 802.3ad LACP fall into
basic LACP functions and extended LACP functions, as described in Table 1-2 .
Table 1-2 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 LACP 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.
Switches of the S5120-SI series that support extended LACP functions can
be used as intermediate devices in LACP MAD implementation