JUNOS Internet Software Network Operations Guide: Hardware
552 ! Understanding Redundant SCGs
Understanding Redundant SCGs
Purpose Inspect redundant SCGs to ensure that they provide a clock signal for the
SONET/SDH interfaces on the router and that they select a clock signal from any
FPC, or from the external clock inputs.
What Are Redundant
SCGs
Two SCGs are installed in the T320 router and the T640 routing node. The SCGs
install into the upper rear of the chassis in the slots labeled
SCG0 and SCG1.
If both SCGs are installed and functioning normally,
SCG0 is master and SCG1 is
backup. Removing the backup SCG does not affect the functioning of the routing
node. Taking the master SCG offline can result in a brief loss of SONET clock lock
while the backup SCG becomes master.
The SCGs are hot-pluggable.
Figure 226 shows the location of the SCGs on the T320 router and the T640 routing
node.
Figure 226: T320 Router and T640 Routing Node Redundant SCG Location
See Also
! Monitoring the Host Subsystem on page 289
! Monitoring Redundant SCGs on page 551
g003268
T320 T640
SCG1
SCG1
SCGs
SCG0
SCG0
SCGs
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