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Link Aggregation Limits and Guidelines Troubleshooting Link Aggregation
page 7-2 OmniSwitch Troubleshooting Guide September 2005
Link Aggregation Limits and Guidelines
Consider the following when configuring Static Link Aggregation groups:
• Maximum number of link aggregation groups: 30 (OmniSwitch 6624/6648), 32 (OmniSwitch 7700/
7800), or 16 (OmniSwitch 8800).
• Number of links per group supported: 2, 4, 8, or 16
• Link aggregation groups are identified by unique MAC addresses, which are created by the switch.
• Load balancing is performed on ingress ports by the link aggregation groups to evenly balance traffic
flows on the physical links.
• The load is to be balanced between parallel links; because of this, Spanning Tree will be shut off on all,
but one link, which belongs to a channel. This port is referred to as the Primary port and the rest of the
ports are Secondary ports.
By default, first-generation Network Interface (NI) modules are not optimized for link aggregation. The
table below shows which NI modules are first-generation modules and are not optimized for link aggrega-
tion. ???? Where is this table, not provided in CS edits. ???? Use the show ni, show module, or show ni
commands to display the part number of the NI module. Second-generation NI modules are distinguished
from first-generation NI modules by "ENI2" or "GNI2" in the part number. (First-generation modules have
ENI, GNI, or 10GNI in their part numbers instead.) If the NI is a second-generation module you do not
need to optimize it.
To modify the optimization status of an NI module use the linkagg slot optimization command. To use
this command, enter linkagg slot followed by the slot number of the NI module then optimization and
either enable or disable. For example, to enable link aggregation optimization on an NI module is Slot 5
enter:
-> linkagg slot 5 optimization enable
When a port is a member of an aggregate group and optimization is enabled on this NI, all bridged traffic
sent from any other port (not part of the aggregate group) on the same switching ASIC to the aggregate
will be dropped. In this case, traffic needs to be routed between that port and the aggregate group. In a
chassis with both first-generation and second-generation NI modules you must configure static link aggre-
gation on all of the first-generation NI modules before you must configure static link aggregation on all of
these NI modules before you configure it on any of the second-generation NI modules. In addition, hot
insertion or hot swapping of a first-generation NI module into a chassis that has only second-generation NI
modules can cause configuration problems.
OmniSwitch 6624/6648 Restrictions
You can create up to 4 link aggregation (both dynamic and static) groups on a single OmniSwitch 6624
switch, up to 8 link aggregation groups on a single 6648 switch, and up to 30 link aggregation groups per
stack. In addition, ports must be configured sequentially and the first port configured must begin with port
number 1, 9, 17, or 25 on an OmniSwitch 6624 or 1, 9, 17, 25, 33, 41, 49, or 51 on an OmniSwitch 6648.
(In a stack, ports on different switches can be assigned to the same dynamic aggregate group.)