3Com 7757 Configuration Manual page 186

186 C 23: L A
HAPTER INK GGREGATION
n
Restriction of I/O
Module Types on Link
Aggregation
n
C
ONFIGURATION
Besides multiple-port aggregation groups, the system is also able to create
single-port aggregation groups, each of which contains only one port. LACP is
enabled on the member ports of dynamic aggregation groups.
Port status of dynamic aggregation group
A port in a dynamic aggregation group can be in one of the two states: selected or
standby. In a dynamic aggregation group, both the selected and the standby ports
can transceive LACPDUs, however, the standby ports cannot forward user packets.
There is a limit on the number of selected ports in an aggregation group.
Therefore, if the number of the member ports that can be set as selected ports in
an aggregation group exceeds the maximum number supported by the device, the
system will negotiate with its peer end, to determine the states of the member
ports according to the port IDs of the preferred device (that is, the device with
smaller system ID). The following is the negotiation procedure:
1 Compare device IDs (system priority + system MAC address) between the two
parties. First compare the two system priorities, then the two system MAC
addresses if the system priorities are equal. The device with smaller device ID will
be considered as the preferred one.
2 Compare port IDs (port priority + port number) on the preferred device. The
comparison between two port IDs is as follows: First compare the two port
priorities, then the two port numbers if the two port priorities are equal; the port
with the smallest port ID is the selected port and the left ports are standby ports.
In an aggregation group, the selected port with the minimum port number serves
as the master port of the group, and other selected ports serve as member ports
of the group.
The down ports in a static aggregation group or dynamic aggregation group
■
are standby ports, which is different in manual aggregation groups.
For the restriction of I/O Module types on link aggregation, refer to Table 120
■
and Table 121.
Table 119 lists link aggregation types and related descriptions.
Type-A modules (I/O Module) include 3C16860, 3C16860, 3C16861, 3C16861,
LS81FS24A, LS81FS24, 3C16858, 3C16858, 3C16859, and 3C16859.