3Com 4800G Series, Configuration Manual

Page: 164 / 1246

164 C
HAPTER
18: 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 aggregations are created manually. After you add a port to a static
aggregation, LACP is enabled on it automatically.
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.
When setting the state of the ports in the local and remote static aggregation
groups, the local and remote systems do the following:
1 Compare their system IDs to identify the higher priority system. (The system ID
comprises LACP priority and system MAC address.)
2 First compare the system LACP priorities. The system with lower system LACP
priority wins out.
3 If the system LACP priorities are the same, compare the system MAC addresses.
The system with the smaller MAC address wins out.
4 Compare the port IDs on the higher priority system. (The port ID comprises port
LACP priority and port number.)
5 Compare the port LACP priorities. The port with lower port LACP priority wins out.
6 If two ports with the same port LACP priority are present, compare their port
numbers. The one with the smaller port ID wins out to become the reference port.
7 Select the candidates for selected ports. To be a candidate, a port must be in the
up state with the same speed, duplex mode, link state, and basic configuration as
the reference port; in addition, their peer ports on the other system must have the
same configuration. All the ports but the selected-port candidates become
unselected.
8 As there is a limit on the number of selected ports, not all selected-port candidates
can become selected ports. Before the limit is reached, all the candidates are set to
the selected state. When the limit is reached, the candidates with lower port
numbers are set to the selected state while the other candidates are set to the
unselected state. At the same time, the other system gets aware of the state
change of the ports on the higher priority system and thus sets the state of the
corresponding local ports.
9 Set the selected port with the lowest port number as the master port in the
aggregation group on each system.
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 reference 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 161.