Mx480 Component Redundancy - Juniper MX480 Hardware Manual

Figure 3: Rear View of a Fully Configured DC-Powered Router Chassis
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MX480 Router Physical Specifications | 178

MX480 Component Redundancy

A fully configured router is designed so that no single point of failure can cause the entire system to fail.
Only a fully configured router provides complete redundancy. All other configurations provide partial
redundancy. The following major hardware components are redundant:
Host subsystem—The host subsystem consists of a Routing Engine functioning together with an SCB.
The router can have one or two host subsystems. If two host subsystems are installed, one functions as
the master and the other functions as the backup. If the master host subsystem (or either of its
components) fails, the backup can take over as the master. To operate, each host subsystem requires a
Routing Engine installed directly into in an SCB.
If the Routing Engines are configured for graceful switchover, the backup Routing Engine automatically
synchronizes its configuration and state with the master Routing Engine. Any update to the master
Routing Engine state is replicated on the backup Routing Engine. If the backup Routing Engine assumes
mastership, packet forwarding continues through the router without interruption. For more information
about graceful switchover, see the Junos OS Administration Library.
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