T640 Component Redundancy - Juniper T640 Hardware Manual

T640 Core Router Hardware Guide

T640 Component Redundancy

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The T640 Core Router is designed so that no single point of failure can cause the entire
system to fail. The following major hardware components are redundant:
Switch Interface Boards (SIBs)—The router has five SIBs. A T640 router that is
connected to a TX Matrix platform requires T640-SIBs ; see
Boards (SIBs) Description" on page
dedicated ASIC with five high-speed links that connect to the SIBs (one link per SIB).
Each Type 3 FPC has two dedicated ASICs, and each ASIC has five high-speed links
that connect to the SIBs (a total of 10 links). Each Type 4 FPC has one dedicated ASIC
with ten high-speed links that connect to the SIBs (two links per SIB). One of the five
SIBs—usually —acts as a backup to the remaining four SIBs. If a SIB fails, the
SIB4
backup SIB becomes active and traffic forwarding continues without any degradation.
When the failed SIB is replaced, it becomes the new backup.
Host subsystem—The host subsystem consists of a Routing Engine functioning together
with a control board. 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 in an adjacent slot to a control board.
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 for Routing Devices.
SONET Clock Generators (SCGs)—The router has a standard configuration of one
SCG. A second can be purchased to function as backup. If one SCG fails, the other
becomes the master SCG. Mastership of the SCGs is independent of the host subsystem,
so routing functions are not affected.
Power supplies—The router has two power supplies, which share the load evenly. If
one power supply fails, the other power supply can provide full power to the router
indefinitely.
Cooling system—The cooling system has redundant components, which are controlled
by the host subsystem. If one of the fans fails, the host subsystem increases the speed
of the remaining fans to provide sufficient cooling for the router indefinitely.
T640 Router Description on page 3
Reinstalling Components in the T640 Chassis on page 123
T640 System Architecture Description on page 5
"T640 Switch Interface
30) Each Type 1 FPC and Type 2 FPC has a
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