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Routing Engines for the M20 and M40e Routers

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.

Routing Engine Components

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

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.

Routing Engines and Routing Engine Panel on the M20 Router

On the M20 router, one or two Routing Engines install into the midplane from the rear of the chassis, as shown in Figure 1. When two Routing Engines are installed, both are powered on, but only one is active (the master); the second Routing Engine is in standby mode and performs no functions. At boot time, both Routing Engines run an arbitration algorithm and elect one as master. By default, the master Routing Engine is in the upper slot (slot 0).

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 replacement instructions, see Replacing the Routing Engine on an M20 Router.

Removal or failure of the standby Routing Engine does not affect router function. If the master Routing Engine is removed from the chassis, the effect depends on whether two Routing Engines are installed:

With the default mastership configuration, if the master Routing Engine experiences 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 M20 Chassis

Image g001112.gif

The M20 router has a Routing Engine panel that is part of the rear fan tray and located immediately to the right of the Routing Engine slots (see Figure 2). The Routing Engine panel contains status LEDs and offline buttons for the Routing Engines.

Figure 2: M20 Routing Engine Panel

Image g001155.gif

Host Module Components on M40e Routers

On M40e routers, each Routing Engine is paired with an MCS (Miscellaneous Control Subsystem) 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 3.

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:

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 3: Rear of M40e Chassis

Image g001948.gif

MCS Description

On M40e routers, the Miscellaneous Control Subsystem (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.

The MCS, in conjunction with the routing software, performs the following functions:

MCS Components

Each MCS (shown in Figure 4) has the following components:

Figure 4: Miscellaneous Control Subsystem

Image g001178.gif

Table 3: States for MCS LEDs

Label

Color

State

Description

MASTER

Blue

On steadily

MCS is master.

OK

Green

On steadily

MCS is functioning normally.

Blinking

MCS is starting up.

FAIL

Amber

On steadily

MCS has failed.

Tools and Parts Required

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

Replacing the Routing Engine on an M20 Router

On an M20 router, one or two Routing Engines install into the midplane from the rear of the chassis, as shown in Figure 1. Each Routing Engine weighs approximately 1.5 lb (0.7 kg).

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 a Routing Engine, see Routing Engines and Routing Engine Panel on the M20 Router.

To replace a Routing Engine in an M20 router, perform the following procedures:

Replacing the Host Module Components on 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 3. 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 on M40e Routers.

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


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