H3C Technologies H3C S12500 Series Switches - Manual (Page 121)

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Table 14 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.
The
smaller the
priority
value, the
higher the
priority. Port aggregation
priority Determines the likelihood of a member port to be selected on a system.
The higher port aggregation priority, the higher likelihood.
3. 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 three times the
LACP timeout interval, the member port assumes that the peer port has failed. You can configure
the LACP timeout interval as the short timeout interval (1 second) or the long timeout interval (30
seconds).
Link aggregation modes
There are two link aggregation modes: dynamic and static. Dynamic link aggregation uses LACP while
static link aggregation does not. A link aggregation group operating in static mode is called a static link
aggregation group, while a link aggregation group operating in dynamic mode is called a dynamic link
aggregation group. Table 15 compares the two aggregation modes.
Table 15 A comparison between static and dynamic aggregation modes
Aggregation
mode
LACP status
on member
ports
Pros Cons
Static Disabled
Aggregation is stable. The
aggregation state of the member
ports is not affected by their peers.
The member ports cannot
change their aggregation state
in consistent with their peers.
The administrator needs to
manually maintain link
aggregations.
Dynamic Enabled
The administrator does not need to
maintain link aggregations. The peer
systems maintain the aggregation
state of the member ports
automatically.
The aggregation state of
member ports is easily affected
by the network environment,
which makes dynamic
aggregation less stable.
In a dynamic link aggregation group:
• A Selected port can receive and send LACPDUs.
• An Unselected port can receive and send LACPDUs only if it is up and have the same class-two
configurations as the aggregate interface.
Aggregating links in static mode
LACP is disabled on the member ports in a static aggregation group. The aggregation state of the
member ports must be maintained manually.