HP VPN Firewall Appliances High Availability Configuration Guide

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• Class-one configurations—Include settings that do not affect the aggregation state of the member
port even if they are different from those on the aggregate interface. Spanning tree settings are
examples of class-one configurations. The class-one configuration of a member port is effective only
when the member port leaves the aggregation group.
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 "A
ggregating 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 "Aggr
egating 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 9 compares the two aggregation modes.
Table 9 A comparison between static and dynamic aggregation modes
Aggregation
mode
LACP status on
memb
er
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.
NOTE:
Only static aggregation groups can be configured in the Web interface.
LACP
IEEE 802.3ad LACP enables dynamic aggregation of physical links. It uses LACPDUs for exchanging
aggregation information between LACP-enabled devices.
1. Basic LACP functions:
Basic LACP functions are implemented through the basic LACPDU fields. These fields include 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.