As of ExtremeXOS 21.1, two different configuration options are available for specifying subsets of active member ports as eligible for distribution. Both of these options specify a subset of the active member ports on a per slot basis. The specific choice of configuration is described in the CLI as a “distribution-mode”. The choice of distribution mode is configurable per LAG (Link Aggregation Group).
The distribution modes below affect only the distribution of known unicast packets on a LAG. Non-unicast packets are distributed among all active members of a LAG.
The “local-slot” distribution mode restricts distribution of unicast packets to the active LAG members on the same slot where the packet was received. If no active LAG members are present on the slot where the packet was received, all active LAG member ports are included in the distribution algorithm.
The “local-slot” distribution mode may be specified during LAG creation with the configure sharing port slot slot distribution-list [port_list | add port_list | all] CLI command. It may also be configured dynamically with the “configure sharing” command. This distribution mode is self-configuring in the sense that no configuration is required other than the specification of the “local-slot” distribution mode. Addition or deletion of LAG member ports via the configure sharing port slot slot distribution-list [port_list | add port_list | all] command is automatically handled.
The “local-slot” distribution mode is useful for reducing the fabric bandwidth load of a switch.
In many SummitStack hardware configurations, the “local-slot” distribution mode will minimize the switching latency of packets distributed to a LAG. Note that some modules may not provide the minimum possible latency due to the details of the switch‘s fabric connections. Some Summit switches have more than one switching ASIC and “local-slot” distribution may still involve inter-ASIC switching through local fabric links.
The “port-lists” distribution mode provides the ability to configure one or more LAG member ports to be eligible for unicast LAG distribution on each slot in the switch. If a slot does not have a distribution port list configured or if none of the configured member ports is active in the LAG, then all active member ports are eligible for unicast distribution.
The “port-lists” distribution mode may be specified during LAG creation with the configure sharing port slot slot distribution-list [port_list | add port_list | all] CLI command. It may also be configured dynamically with the configure sharing port slot slot distribution-list [port_list | add port_list | all]command. The use of the “port-lists” distribution mode should be taken into consideration when adding ports to a LAG with the “configure sharing” CLI command. Any newly added port on a LAG will not be available for unicast distribution unless it is also added to the distribution port list of at least one slot.
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