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Understanding the QFabric System Control Plane

The control plane in the QFabric system transports management traffic between QFabric system components to facilitate system operations, configuration, and maintenance. This topic covers:

Control Plane Elements

Control traffic within a QFabric system is carried across a redundant, scalable, out-of-band, Ethernet switching network called the control plane network. To maintain high availability, the QFabric system control plane is separated from the QFabric system data plane. Figure 1 shows a diagram of the QFabric system devices that compose the control plane network.

Figure 1: QFabric System Control Plane NetworkQFabric System Control Plane Network

The control plane consists of the following elements:

  • Control plane switches—Provide connectivity to the management interfaces of all QFabric system components in the control plane network, including the Node devices, the Interconnect devices, and the Director group. When you interconnect all QFabric system devices to the control plane switches, the Director group can manage the entire system. Depending on the size and scale of your QFabric system, the control plane switches might be standalone switches or might be groups of switches bundled into a Virtual Chassis (See the Example topics in the Related Documentation section of this topic to learn more about the control plane switch configuration required for your QFabric system.)

    For example, the control plane for the QFX3000-G QFabric system requires two Virtual Chassis containing either four EX4200 switch members or four EX4300 switch members each. The two Virtual Chassis connect to each other across a 10-Gigabit Ethernet LAG link to provide maximum resiliency for the QFabric system control plane. The control plane for the QFX3000-M Qfabric system requires either two EX4200 switches or two EX4300 switches, interconnected and configured in a LAG for redundancy.

    Note:

    You cannot mix EX4200 switches and EX4300 switches in the control plane in a QFabric system.

  • Connections between the management interfaces of the Node devices and the control plane switches—Enable control plane connectivity from the Node devices to the rest of the QFabric system. You must connect two management interfaces from each Node device to the control plane switches. Connect each interface to a different control plane switch to provide system resiliency.

  • Connections between the management interfaces of the Interconnect devices and the control plane switches—Enable control plane connectivity from the Interconnect devices to the rest of the QFabric system. You must connect the interfaces in each Interconnect device to the control plane switches. Connect each interface to a different control plane switch to provide system resiliency.

    For example, on QFX3008-I Interconnect devices in a QFX3000-G QFabric system, there are two Control Boards and two interfaces per Control Board, for a total of four connections per Interconnect device. To provide system resiliency, connect one interface from each Control Board to the first control plane Virtual Chassis, and connect the second interface from each Control Board to the second control plane Virtual Chassis.

  • Connections between the network module interfaces of the Director group and the control plane switches—Enable control plane connectivity from the Director group to the rest of the QFabric system. You must connect some interfaces from the first network module in a Director device to one control plane switch, and connect some interfaces from the second network module in a Director device to the second control plane switch. Also, you must connect the ports from the first network module to the primary control plane switch for each Director device (which may vary depending on the configuration of your Director group).

    For guidance on the QFabric control plane configuration and cabling recommendations, see:

  • Routing Engines—Although they are automatically provisioned, specialized Routing Engines implement services such as default QFabric system infrastructure, device management, route sharing, and diagnostics to support the QFabric system. Routing Engines for control plane functions are virtual entities that run on the Director group.

  • Fabric management protocol—A link-state protocol runs on the control plane network to identify and initialize QFabric system resources, support device redundancy, and support management communication throughout the QFabric system. The protocol is enabled by default.

Control Plane Services

The QFabric system control plane provides the infrastructure to support the following services for the QFabric system:

  • System initialization

  • Topology discovery

  • Internal IP address and unique ID assignment

  • Route information sharing

  • Configuration delivery to Node devices

  • Interdevice communication between Node devices, Interconnect devices, and the Director group

Many of these services are provided by the external Routing Engines that run in software on the Director group.