JUNOS Internet Software Network Operations Guide: Hardware
106 ! Understanding Key Router Components
The Routing Engine constructs and maintains one or more routing tables (see
Figure 23). From the routing tables, the Routing Engine derives a table of active
routes, called the forwarding table, which is copied into the Packet Forwarding
Engines. The design of the T-series Internet Processor allows the forwarding table in
the Packet Forwarding Engines to be updated without interrupting the router’s
forwarding.
Figure 23: Control Packet Handling for Routing and Forwarding Table Update
On the M320 and T320 routers and the T640 routing node, the host subsystem
provides the routing and system management functions. The host subsystem
consists of the Routing Engine and the Control Board. For more information about
the host subsystem, see “Monitoring the Host Subsystem” on page 289. For more
information about the Control Boards, see “Monitoring the Control Board” on
page 301.
On the M40e and M160 routers, the host module provides the routing and system
management functions. The host module consists of the Routing Engine and the
Miscellaneous Control Subsystem (MCS). For more information about the host
module, see “Monitoring the Host Module” on page 341. For more information
about the MCS, see “Monitoring the MCS” on page 359.
On the M10i router, the Routing Engine works with its companion High-Availability
Chassis Manager (HCM) to provide control and monitoring functions for router
components. For more information about the HCM, see “Monitoring the HCM” on
page 431.
Packets
in
Packets
out
Packet Forwarding
Engines
Forwarding table
Forwarding table
updates
Routing protocol
packets from network
Routing Engine
Routing protocol
process
1240
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