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Segregating QFabric Traffic Flows With Flow Groups

In a QFabric system, a hash function is used to select an Interconnect device to forward traffic between two ingress switches, which are called Node devices. Since this hash function is performed on all Interconnect devices, it is possible for redundant multicast streams to flow through one Interconnect device, making that Interconnect device a potential single point of failure for the redundant flows. Some operations, such as financial transactions, require redundant data flows to use different Interconnect devices to avoid point-of-failure data loss. To enforce this in a fabric, you can create a flow group for multicast or unicast traffic from a particular ingress switch. In a flow group, switches are forced to use different, specified Interconnect devices to forward redundant traffic.

Note:

An Interconnect device can belong to only one flow group but can serve as a backup to other flow groups.

To direct redundant QFabric system traffic flows to different Interconnect devices:

  1. Create a flow group and indicate the Node device where the redundant data originates:
  2. Indicate at least one Interconnect device connected to the switch to be used for redundancy:

    If all redundant data from the named switch will use the flow group, you are finished with the configuration.

  3. You can alter a flow group’s configuration by overriding the software’s Node device preferences for Interconnect devices. Interconnect devices that reside in the default group (those that are not assigned to a user-configured flow group) have a link preference value set to normal in the software. When you create a flow group, the flow-groups configuration statement resets some Interconnect devices’ preference to high (for those assigned to a flow group) and others to never (for those assigned to a different flow group) to create the flow.
    • To add a Node device to multiple flow groups, set the link between the Node device in the original flow group and a different Interconnect device to high:

    • To configure a Node device to use an Interconnect device from a different flow group if none in the same flow group are available, set the link between the Node device and the other group’s Interconnect device to normal:

    • To increase the priority of a switch for Interconnect devices, set the switch’s Interconnect device link preference to high.

    • To prevent a flow group’s switches from using an Interconnect device, set the Interconnect device link preference to never.

For an example of flow group configuration, see Example: Creating a QFabric Flow Group.

Tip:

To add a TOR to multiple flow groups:

set fabric resources node-device TOR-B interconnect-device IC-A preference HIGH

To configure a TOR to use an Interconnect device from a different flow group if none in the same flow group are available:

set fabric resources node-device TOR-B interconnect-device IC-A preference NORMAL

To increase the priority of default-flowgroup Interconnect devices for a specific TOR:

set fabric resources node-device TOR-A interconnect-device ALL_ICS preference HIGH

To configure default-flowgroup TORs to never use a particular Interconnect device:

set fabric resources node-device ALL_TORS interconnect-device IC-A preference NEVER