Step 2: Check the SIB Fuses
The M320 router requires fuses for the SIBs. The fuses for the Control Board, SIBs, and FPCs are located in the rear of the midplane behind the power supply in slot PEM0. When the fuse for an SIB blows, the SIB stops functioning even though it is installed correctly and the power supplies are providing power to the router.
Figure 137 shows the location of the fuses in the rear of the midplane for the SIBs. (The labels shown in the figure do not appear on the actual fuses—the clear cover on every fuse reads BUSS GMT-X—and might not match the labels on the midplane. Ignore the labels on the midplane.)
