3Com MSR 50 Series, Configuration Manual

Page: 348 / 2443

348 C
HAPTER
15: L
INK
A
GGREGATION
O
VERVIEW
When the configuration of some port in a manual aggregation group changes, the
system does not remove the aggregation; instead, it re-sets the
selected/unselected state of the member ports and re-selects a master port.
Static LACP Link
aggregation
Overview
Static aggregation groups are created manually. Adding a port to a static
aggregation group also enables LACP on it.
Port states in static aggregation
In a static aggregation group, ports can be selected or unselected, where both can
receive and transmit LACPDUs but only selected ports can receive and transmit
data frames. The selected port with the lowest port number is the master port and
all others are member ports.
All member ports that cannot aggregate with the master are placed in unselected
state. These ports include those using the basic configurations different from the
master port or those located on a board different from the master port because of
the cross-board aggregation restriction.
Member ports in up state can be selected if they have the configuration same as
that of the master port. The number of selected ports however, is limited in a static
aggregation group. When the limit is exceeded, the local and remote systems
negotiate the state of their ports as follows:
1
Compare the actor and partner system IDs that each comprises a system LACP
priority plus a system MAC address as follow:
■
First compare the system LACP priorities. The system with lower system LACP
priority wins out.
■
If they are the same, compare the system MAC addresses. The system with the
smaller ID has higher priority. (the lower the LACP priority, the smaller the MAC
address, and the smaller the device ID)
2
Compare the port IDs that each comprises a port LACP priority and a port number
on the system with higher ID as follows:
■
Compare the port LACP priorities. The port with lower port LACP priority wins
out.
■
If two ports with the same port LACP priority are present, compare their port
numbers. The state of the ports with lower IDs then change to selected and the
state of the ports with higher IDs to unselected, so does the state of their
corresponding remote ports. (the lower the LACP priority, the smaller the port
number, and the smaller the port ID)
n
The maximum number of selected ports in a static aggregation group varies by
device.
Port configuration considerations in static aggregation
Like in a manual aggregation group, in a static LACP aggregation group, only
ports with configurations consistent with those of the master port can become
selected. These configurations include port rate, duplex mode, link state and other
basic configurations described in
“Consistency Considerations for Ports in an
Aggregation” on page 346 ."