3Com S7902E, Руководство по настройке

Страница: 58 / 2621

1-2
Aggregation group
An aggregation group is created automatically when you create an aggregate interface and is
numbered the same as the aggregate interface. You can assign Ethernet interfaces to the aggregate
group to create a link aggregation but the type of Ethernet interface assignable to the group depends on
the type of the aggregate interface:
z
If the aggregate interface is a Layer 2 interface, a Layer 2 aggregation group is created. You can
assign only Layer 2 Ethernet interfaces to the group.
z
If the aggregate interface is a Layer 3 interface, a Layer 3 aggregation group is created. You can
assign only Layer 3 Ethernet interfaces to the group.
Current device only supports Layer 2 aggregation group.
States of the member ports in an aggregation group
A member port in an aggregation group can be in one of the following two states:
z
Selected: a selected port can forward user traffic.
z
Unselected: an unselected port cannot forward user traffic.
The rate of an aggregate interface is the sum of the selected member ports’ rates. The duplex mode of
an aggregate interface is consistent with that of the selected member ports. Note that all selected
member ports use the same duplex mode.
For how the state of a member port is determined, refer to Static aggregation mode and Dynamic
aggregation mode.
IEEE 802.3ad LACP protocol
The IEEE 802.3ad Link Aggregation Control Protocol (LACP) enables the dynamic aggregation of
physical links and uses link aggregation control protocol data units (LACPDUs) for information
exchange between LACP-enabled devices. With the usage of expansion fields in LACPDUs, LACP can
deliver extended functions in addition to its basic functions.
1) Basic LACP functions
Basic LACP functions are achieved with the basic fields in LACPDUs, which cover information including
system LACP priority, system MAC address, port LACP priority, port number, and operational key. With
LACP enabled on a port, LACP sends the above information of the port to its peer via LACPDUs. Upon
receiving an LACPDU, the peer compares the received information with the information received on
other ports. This allows the two systems to reach an agreement on which link aggregation member
ports should be placed in the selected state.
2) Extended LACP functions
By using expansion fields in LACPDUs, you can expand the functions of LACP. For example, by
defining a new Type/Length/Value (TLV) data field among the expansion fields of the LACPDUs, you
can deliver the LACP multi-active detection (MAD) mechanism in an Intelligent Resilient Framework
(IRF).