R0106-HP MSR Router Series Layer 2 - LAN Switching Configuration Guide(V7)

16
LACP functions
Basic LACP functions are implemented through the basic LACPDU fields, including the system LACP
priority, system MAC address, port priority, port number, and operational key.
LACP operating modes
LACP can operate in active or passive mode.
When LACP is operating in passive mode on a local member port and its peer port, both ports cannot
send LACPDUs. When LACP is operating in active mode on the port on either end of a link, both ports
can send LACPDUs.
LACP priorities
LACP priorities include system LACP priority and port priority, as described in Table 2. The smaller the
priority value, the higher the priority.
Table 2 LACP priorities
T
yp
e Descri
p
tion
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. The system that has lower priority sets port
state accordingly.
Port priority
Determines the likelihood of a member port to be selected on a system. The higher port
priority, the higher the likelihood of selection.
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 the LACP timeout interval, the
member port assumes that the peer port has failed.
The LACP timeout interval also determines the LACPDU sending rate of the peer. You can configure the
LACP timeout interval as the short timeout interval (3 seconds) or the long timeout interval (90 seconds).
If you configure the short timeout interval, the peer sends LACPDUs fast (one LACPDU per second). If you
configure the long timeout interval, the peer sends LACPDUs slowly (one LACPDU every 30 seconds).
How dynamic link aggregation works
Choosing a reference port
The system chooses a reference port from the member ports that are in up state and have the same
attribute configurations as the aggregate interface. A Selected port must have the same operational key
and attribute configurations as the reference port.
The local system (the actor) and the remote system (the partner) negotiate a reference port by using the
following workflow:
1. The systems compare their system IDs. (A system ID contains the system LACP priority and the
system MAC address.) The lower the LACP priority, the smaller the system ID. If LACP priority
values are the same, the two systems compare their MAC addresses. The lower the MAC address,
the smaller the system ID.
2. The system with the smaller system ID chooses the port with the smallest port ID as the reference
port. (A port ID contains a port priority and a port number.) The port with the lower priority value