Routing Engine

The Routing Engine is an Intel-based PCI platform that runs JUNOS Internet software. Software processes that run on the Routing Engine maintain the routing tables, manage the routing protocols used on the router, control the router's interfaces, control some chassis components, and provide the interface for system management and user access to the router.

For a description of the Routing Engine's role in router architecture, see Routing Engine Architecture.

One or two host modules (paired Routing Engine and MCS) can be installed into the midplane from the rear of the chassis, as shown in Figure 3. If two host modules are installed, the Routing Engines together determine which is the master and which is in standby mode (and so performs no functions). By default, the Routing Engine in the slot labeled RE0 is the master. The master Routing Engine also determines which of the two PCGs is the master.

The Routing Engine is hot-pluggable, as described in Field-Replaceable Units (FRUs). For information about the effect of removing a Routing Engine, see Host Module. For replacement instructions, see Replacing a Routing Engine.

Routing Engine Components

The Routing Engine (shown in Figure 9) is a two-board system with the following components:

• CPU—Runs JUNOS Internet software to maintain the router's routing tables and routing protocols. It has a Pentium-class processor.
• SDRAM—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 drive is fixed and inaccessible from outside the router.
• Hard disk—Provides secondary storage for log files, memory dumps, and rebooting the system if the flash drive fails.
• PC card slots—Accept removable PC cards, which store software images for system upgrades.
• LED—Indicates disk activity for the internal IDE interface. It does not necessarily indicate routing-related activity.
• Interfaces for out-of-band management access—Provide information about Routing Engine status to devices (console, laptop, or terminal server) that can be attached to access ports located on the Connector Interface Panel (CIP).
• EEPROM—Stores the serial number of the Routing Engine.
• Reset button—Reboots the Routing Engine when pressed.

The LEDs that report host module status (and by implication Routing Engine status) are on the craft interface rather than the Routing Engine faceplate. For more information, see Host Module LEDs.

The appearance and position of electronic components or the PC card slot on your Routing Engine might differ from Figure 9 and other figures in this document that depict the Routing Engine. These differences do not affect Routing Engine installation and removal or functionality.

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

If two Routing Engines are installed, they must both be the same version.