Routing Engine Components; Figure 10: M120 Routing Engine - Juniper Networks Hardware Manual

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NOTE: If two Routing Engines are installed, they must both be the same
hardware model.
There is a USB memory device that connects directly into the front of Routing Engine.
The USB port allows you to plug in a USB keychain device.

Figure 10: M120 Routing Engine

Routing Engine Components on page 19
Routing Engine Boot Sequence on page 20

Routing Engine Components

Each Routing Engine (shown in Figure 10 on page 19) consists of the following
components:
CPU—Runs Junos OS to maintain the router's routing tables and routing protocols. It
has a Pentium-class processor.
DRAM—Provides storage for the routing and forwarding tables and for other Routing
Engine processes.
USB port—Provides a removable media interface through which you can install the
Junos OS manually. See Figure 11 on page 20. Junos supports USB version 1.0.
CompactFlash card—Provides primary storage for software images, configuration files,
and microcode. The disk is a fixed compact flash and is inaccessible from outside the
router.
Hard disk—Provides secondary storage for log files, memory dumps, and rebooting the
system if the CompactFlash card fails.
LED—Indicates disk activity for the internal IDE interface. It does not necessarily indicate
routing-related activity.
NOTE: The LEDs that report host module status (including Routing Engine
status) are on the craft interface rather than the Routing Engine faceplate.
HDD LED—Indicates disk activity for the hard disk drive.
Chapter 2: M120 Hardware Components
19