R3303-HP HSR6800 Routers Layer 2 - LAN Switching Configuration Guide

7
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. For information about how a reference port is chosen in a static link
aggregation group, see "Choosing a reference port" in the
section "Aggregating links in static mode."
For information about how a reference port is chosen in a dynamic link aggregation group, see
"Choosing a reference port" in the sec
tion "Aggregating links in dynamic mode."
Link aggregation modes
Link aggregation can be done in dynamic mode or static mode. Dynamic link aggregation uses the IEEE
802.3ad LACP, but static link aggregation does not. Table 2 c
ompares the two aggregation modes.
Table 2 A comparison between static and dynamic aggregation modes
Aggregation
mode
LACP status on
member
p
orts
Pros Cons
Static Disabled
Aggregation is stable. Peers do
not affect the aggregation state of
member ports.
Member ports do not
automatically align their
aggregation state with their peer
ports. The administrator must
manually maintain link
aggregations.
Dynamic Enabled
The peer systems maintain the
aggregation state of member
ports automatically.
Aggregation is unstable. The
aggregation state of member
ports is susceptible to network
changes.
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 has the same class-two configurations as the
aggregate interface.
LACP
1. LACP functions
IEEE 802.3ad LACP offers basic LACP functions and extended LACP functions, as shown in Table
3.
Table 3 Basic and ext
ended 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 other
member ports. In this way, the two systems reach an agreement on which ports
should be placed in Selected state.