On J2320 and J2350 routers, an external compact flash, also known as removable compact flash, accepts a type I or II compact flash, as defined in the CompactFlash Specification published by the CompactFlash Association. The J2320 and J2350 chassis has a slot on the rear for external compact flashes (see Figure 3). When the external compact flash is installed and configured, it automatically acts as the secondary boot device if the internal compact flash fails on startup.
Depending on the capacity of the external compact flash, you can also configure it to receive any core files generated during a failure. For information about configuring an external compact flash, see the J-series Services Router Administration Guide.