Routing Engines for the M40e Router

The Routing Engine is an Intel-based PCI platform that runs JUNOS 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.

Routing Engine Components

Each Routing Engine is a two-board system with the following components:

• CPU—Runs JUNOS software 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.
• Internal flash disk—Provides primary storage. It accommodates the software image, up to 49 configuration files, and the microcode. This is a fixed compact flash disk and is inaccessible from outside the router.
• Hard disk—Provides secondary storage for log files, memory dumps, and rebooting the system if the internal flash disk fails.
• PC Card slot—Accepts a removable PC Card, which stores software images for system upgrades.
• Interfaces for out-of-band management access—Provide information about Routing Engine status to devices that can be attached to external access ports. On M40e routers, the access ports are located on the Connector Interface Panel (CIP).

  Each Routing Engine has one 10/100-Mbps Ethernet port for connecting to a management network, and two asynchronous serial ports—one for connecting to a console and one for connecting to a modem or other auxiliary device.

• EEPROM—Stores the serial number of the Routing Engine.
• LED—Indicates disk activity for the internal IDE interface. It does not necessarily indicate routing-related activity.

  On the M40e router, the LEDs that report Routing Engine, host module, or host subsystem status are on the craft interface. For more information, see the hardware guide for your router.

• Reset button—Reboots the Routing Engine when pressed.
• Extractor clips—Control the locking system that secures the Routing Engine in the chassis.

  Note: The appearance and position of electronic components or the PC Card slot on your Routing Engine might differ from those in the figures in this document. These differences do not affect Routing Engine installation and removal or functionality. For specific information about components in your Routing Engine (for example, the capacity of the hard disk), issue the show chassis routing-engine command.

The boot sequence for the three storage media is as follows: the PC Card (if present), then the internal flash disk (if present), then the hard disk.

Host Module Components in M40e Routers

On M40e routers, each Routing Engine is paired with a Miscellaneous Control Subsystem (MCS) in a functional unit called a host module. (For more information about the MCS, see MCS Description.) One or two host modules can be installed into the midplane from the rear of the chassis, as shown in Figure 1.

When two host modules are installed in the router, both are powered on, but only one is active (the master). At boot time, both Routing Engines run an arbitration algorithm and elect one as master. The second host module is in standby mode and performs no functions. By default, the master host module is the one with components installed in the slots labeled RE0 and MCS0. You can change the default mastership by including the appropriate routing-engine statement at the [edit chassis redundancy] hierarchy level in the configuration, as described in the JUNOS System Basics Configuration Guide.

The host module components are hot-pluggable. Removal or failure of either or both components in the standby host module does not affect router function. If one or both components in the master host module are removed from the chassis, the effect depends on whether two host modules are installed:

• If there is only one host module, packet forwarding halts until both the Routing Engine and MCS are reinstalled and functioning normally.
• If there are two host modules, packet forwarding halts while the standby host module becomes the master and the new master Routing Engine resets the Packet Forwarding Engine.

With the default mastership configuration, if one or both components in the master host module experience a hardware or software failure, you must correct the problem manually. You can issue the appropriate request chassis routing-engine master command to switch mastership to the other Routing Engine, for example. (For more information, see the JUNOS System Basics and Services Command Reference.)

You can configure the router so that the standby Routing Engine automatically assumes mastership if it stops receiving keepalive signals from the master. In JUNOS Release 7.0R1 and later, you can also configure automatic mastership switchover for other problems that occur on the master Routing Engine, such as a hard disk failure. For more information, see the section about Routing Engine redundancy in the JUNOS System Basics Configuration Guide.

Figure 1: Rear of M40e Chassis

MCS Description

On M40e routers, the MCS works with its companion Routing Engine to provide control and monitoring functions for router components. It also generates a clock signal for the SONET/SDH interfaces on the router.

In conjunction with the routing software, the MCS performs the following functions:

• Monitoring and control of router components—The MCS collects statistics from all sensors in the system. When it detects a failure or alarm condition, it sends a signal to the Routing Engine, which generates control messages or sets an alarm. The MCS also relays control messages from the Routing Engine to the router components.
• Controlling component power-up and power-down—The MCS controls the power-up sequence of router components as they start, and powers down components when their offline buttons are pressed.
• Signaling of mastership—In a router with more than one host module, the MCS signals to all router components which host module is the master and which is the standby. It relays the mastership signal for the two Packet Forwarding Engine Clock Generators (PCGs) as well.
• Providing SONET/SDH clock source—The MCS generates a 19.44-MHz SONET/SDH clock signal, along with a signal that indicates which MCS is the master SONET/SDH clock generator (if two MCSs are installed).
• Clock monitoring—The MCS monitors the PCG system clock and its SONET/SDH clock to verify that they are providing the expected signal. It generates an alarm if a clock signal is incorrect.
• Control of Flexible PIC Concentrator (FPC) resets—If the MCS detects errors in an FPC, it attempts to reset the FPC. After three unsuccessful reset attempts, the MCS takes the FPC offline and informs the Routing Engine. Other FPCs are unaffected, and system operation continues.

MCS Components

Each MCS (shown in Figure 2) has the following components:

• PCI interface—Connects the MCS to the Routing Engine.
• 100-Mbps Ethernet switch—Carries signals and monitoring data between router components.
• 19.44-MHz stratum 3 reference clock—Generates clock signal for SONET/SDH PICs.
• I²C controller—Monitors the status of router components.
• Three LEDs—Indicate MCS status. There is a blue one labeled MASTER, a green one labeled OK, and an amber one labeled FAIL. Table 3 describes the LED states.
• Offline button—Prepares the MCS for removal from the router when pressed.
• Extractor clips—Control the locking system that secures the MCS in the chassis.

Figure 2: Miscellaneous Control Subsystem

Table 3: States for MCS LEDs

Tools and Parts Required

To replace a Routing Engine or an MCS, you need the following tools and parts:

• Electrostatic bag or antistatic mat
• Electrostatic discharge (ESD) grounding wrist strap
• Phillips (+) screwdriver, number 2

Replacing the Host Module Components in an M40e Router

On an M40e router, one or two host modules install into the midplane from the rear of the chassis, as shown in Figure 1. Each host module consists of a paired Routing Engine and MCS installed in adjacent slots (labeled MCS0` and RE0 or RE1 and MCS1 from top to bottom).

If the host system is redundant, the backup Routing Engine is hot-removable and hot-insertable, but the master Routing Engine is hot-pluggable. A Routing Engine that is not redundant is hot-pluggable. For a description of the effect of removing one or both components, see Host Module Components in M40e Routers.

To replace the host module components in an M40e router, perform the following procedures:

• Switching Host Module Mastership on an M40e Router
• Replacing a Routing Engine in an M40e Router
• Replacing an MCS in an M40e Router