J4300 and J6300 Routing Engine

The Routing Engine provides three main functions:

• Creates the packet forwarding switch fabric for the Services Router, providing route lookup, filtering, and switching on incoming data packets, then directing outbound packets to the appropriate interface for transmission to the network.
• Maintains the routing tables used by the router and controls the routing protocols that run on the router.
• Provides control and monitoring functions for the router, including controlling power and monitoring system status.

The Routing Engine consists of the following components:

• Processor—Creates the packet forwarding switch fabric for the router and runs JUNOS Internet software to maintain the router's routing tables and routing protocols. The Routing Engine has a Pentium-class processor.
• DRAM—Buffers incoming packets and provides storage for the routing and forwarding tables and for other Routing Engine processes.
• Compact flash drive—Provides primary storage for software images, configuration files, and microcode. The compact flash drive is accessible from the rear of the router, and is field-replaceable. For information about replacing the compact flash drive, see Removing and Installing the Primary Compact Flash Disk.
• PCI bus—Provides the interface to the PIMs.
• EPROM—Stores the serial number of the Routing Engine.

For specific information about Routing Engine components (for example, the amount of DRAM installed), issue the show chassis routing-engine command.

J4300 and J6300 Boot Devices

The J4300 and J6300 Services Routers can boot from three devices:

• Primary compact flash disk
• Removable compact flash disk
• USB storage device

J4300 and J6300 Boot Sequence

Normally, the Services Router boots from the primary compact flash disk. If the compact flash disk fails, the router attempts to boot from the removable compact flash disk, which is the alternate boot device. If the removable compact flash disk is not present or fails, the router attempts to boot from the USB storage device.