Specifications

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Component Redundancy
The router is designed so that no single point of failure can cause the entire
system to fail. The following major hardware modules are redundant:
§ Host module—Comprises a Routing Engine and SCB functioning
together. The router can have one or two host modules.
§ Power supplies—The router has two power supplies, which share the
load evenly. If one of the power supplies fails, the second power supply
can supply full power to the router’s components.
§ Cooling system—The front and rear cooling subsystems have redundant
components, which are controlled by the SCB. If an impeller or fan fails,
the SCB increases the speed of the remaining impellers and fans to
provide sufficient cooling for the unit indefinitely.
Chassis
The router chassis is a rigid sheet metal structure that houses all the other router
hardware components. The chassis is 35 in. (89 cm) high, 19 in. (38 cm) wide,
and 23.5 in. (60 cm) deep. The chassis mounting system installs into standard
19-in. equipment racks or Telco center-mounted racks and allows two routers to
be installed into one standard, 78-in. rack.
The chassis contains the following components:
§ Two electrostatic discharge points (banana plug receptacles), one front
and one rear
§ Front-mounting metal ears on either side, used to bolt the chassis to the
rack
§ 19” rack-mounting ears for Telco center rack mounting.
§ Front-mounting ears have protectors when the chassis is center
mounted.
Routing Engine
The Routing Engine consists of JUNOS Internet software running on an Intel-
based PCI platform. The Routing Engine is located in the rear of the M40 router
chassis. The Routing Engine module is housed in a metal case that is equipped
with handles to facilitate installation and removal from the chassis. The Routing
Engine module installs into the rear of the M40 router chassis, in a compartment
behind the card cage.
The Routing Engine is field-replaceable and hot-pluggable. The Routing Engine
consists of the following hardw are components:
§ System processors
o Motherboard, with a Pentium processor that runs the JUNOS
software.
o Ethernet board for internal communication between the Routing
Engine and the Packet Forwarding Engine.
§ Storage components
o 256-MB DRAM—Provides storage for the routing and
forwarding tables.
o 80-MB flash disk—Provides primary storage for router software
images. It can hold two images, two configurations files, and
microcode.
o 6.4-GB IDE hard disk—Provides secondary storage for
rebooting the system in the event of a flash disk failure, as well
as providing storage for memory dumps.
o 120-MB LS-120 drive—Provides alternate secondary storage.
The same shape and size as the standard 1.44-MB 3.5-inch
diskette, the LS-120 disk holds 120 MB of data and can be
used for installing software images and configurations.
§ System interfaces
o 100-Mbps internal connection to the M40 router System Control
Board—Connects the Routing Engine to the Packet Forwarding
Engine.