Understanding Routing Engines in the QFabric System


Routing Engines perform many important processing tasks in the QFabric system. Knowing where the Routing Engines are located and what services they provide enables you to troubleshoot the QFabric system and ensure that it is running the way it should.

Hardware-Based Routing Engines

A traditional Juniper Networks Routing Engine is a hardware field-replaceable unit that runs routing protocols, builds the routing and switching tables, sends routing information to the Packet Forwarding Engine, and handles several software processes for the device (such as interface control, chassis component monitoring, system management, and user access). Node devices that are part of server Node groups in the QFabric system that connect to servers or storage devices implement Routing Engine functions locally using this traditional hardware method.

Software-Based External Routing Engines

The QFabric system also uses external Routing Engines that run in software on the Director group. In contrast with traditional Routing Engines, the functions and processes provided by software-based Routing Engines are segmented, specialized, and distributed across multiple Routing Engine instances running on the Director group. Such separation provides redundancy for these functions and enables the QFabric system to scale. Figure 1 shows the external Routing Engine types.

Figure 1: External Routing Engine Types
External Routing Engine

These special-purpose external Routing Engine instances running on the Director group provide the following major services for the QFabric system:

  • Fabric manager Routing Engine—Provides services to all devices in the QFabric system, such as system initialization, topology discovery, internal IP address and ID assignment, and interdevice communication. The fabric manager Routing Engine authenticates Interconnect and Node devices, and maintains a database for system components. A single fabric manager Routing Engine instance is generated to manage the entire QFabric system.

  • Fabric control Routing Engine—Runs the fabric control protocol to share route information between available devices in a partition. A pair of redundant route distribution Routing Engine instances is generated for every partition in the QFabric system, and both instances are active.

  • Diagnostic Routing Engine—Gathers operational information that allows QFabric system administrators to monitor the health of the QFabric system. A single Routing Engine instance is generated for the entire QFabric system.

  • Network Node group Routing Engine—Provides Routing Engine functionality for groups of Node devices bundled together as a single Layer 3 routing device, which is used to connect to external networks. A pair of redundant Routing Engine instances is generated for every network Node group in the QFabric system.