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.
Figure 226 shows the location of the SCGs on the T320 router and the T640 routing node.
