Hardware Components
Each Juniper Networks router consists of a chassis and a set of components, including FPCs, PICs, Routing Engines, power supplies, cooling system, and cable management system. Many of the components are field-replaceable units. The following major components are discussed in this topic:
Chassis
Chassis dimensions are listed in the physical specifications table for each router. For more information about chassis dimensions, see the router platform-specific hardware guide.
Each Juniper Networks router features a rigid sheet metal chassis that houses all of the router components. The chassis are designed to install into a variety of racks, including standard 19-inch equipment racks, telco center-mount racks, and four-post racks and cabinets. See Table 1 for the maximum number of each router type that can be installed into a rack. Each chassis includes mounting ears or support posts to facilitate rack mounting, and one or more points for connecting an electrostatic discharge (ESD) wrist strap for use when servicing the router.
Table 1: Maximum Number of Routers per Rack
Router or Routing Node | Maximum in Standard Rack |
|---|---|
T640 | 2 |
T320 | 3 |
M160 | 2 |
M40e | 2 |
M40 | 2 |
M20 | 5 |
M5 and M10 | 14 |
Each chassis includes a midplane (called the backplane on an M40 router). The midplane transfers data packets to and from the FPCs, distributes power to router components, and provides signal connectivity to the router components for system monitoring and control.
Flexible PIC Concentrators
The FPCs house the PICs used in the router and connect them to other router components. FPCs install into the front of the router in either a vertical or horizontal orientation, depending on the router. A compatible FPC can be installed into any available FPC slot, regardless of the PICs it contains. If a slot is not occupied by an FPC, a blank FPC panel must be installed to shield the empty slot and allow cooling air to circulate properly through the FPC card cage. For information about FPCs, see the specific hardware guide.
Physical Interface Cards
Juniper Networks M-series routers and T-series platforms use PICs to connect to a wide variety of network media. PICs receive incoming packets from the network and transmit outgoing packets to the network, performing framing and line-speed signaling for their specific media type. Before transmitting outgoing data packets, the PICs encapsulate the packets received from the FPCs. Each PIC is equipped with an ASIC that performs control functions specific to the PIC’s media type. For information about PICs, see the specific PIC guide.
Routing Engine
The Routing Engine consists of an Intel-based PCI platform running the Junos OS. The Routing Engine maintains the routing tables used by the router in which it is installed and controls the routing protocols on the router. The T640 routing node, and the T320, M160, M40e, and M20 routers support up to two Routing Engines, while the M40, M10, and M5 routers support a single Routing Engine.
Each Routing Engine consists of a CPU; SDRAM for storage of the routing and forwarding tables and other processes; a compact flash disk for primary storage of software images, configuration files, and microcode; a hard disk for secondary storage; a PC card slot (on some M40 routers, a floppy disk) for storage of software upgrades; and interfaces for out-of-band management access.
Power Supplies
Each Juniper Networks M-series router, T-series platform, or MX-series router has one to four load-sharing power supplies depending on the platform. If a power supply in a redundant configuration is removed or fails, the other power supplies assume the electrical load. For more information about the power supplies in each router, see the router platform-specific hardware guide.
The power supplies are connected to the router midplane, which distributes the different output voltages throughout the router and its components. Some routers can operate using either AC or DC power; other routers operate with DC power only. For information about the type of power used by each router, see the platform-specific hardware guide.
Cooling System
Each Juniper Networks M-series router and T-series platform features a cooling system designed to keep all router components within recommended operating temperature limits. If one component of the cooling system fails or is removed, the system automatically adjusts the speed of the remaining components to keep the temperature within the acceptable range. The cooling system for each router is unique and can consist of fans, impellers, and air filters. For information about the cooling system components of each router, see the “Major Hardware Components” table in the router platform-specific hardware guide.