This reports the current number of bytes from the device's Processor Memory Pool that CEF has allocated for its own use, FIB, adjacency tables, on this managed entity. Because CEF's FIB size scales directly with the number of routes it holds, this gauge climbing steadily over time, especially in step with growing BGP table size, is a specific, trackable early-warning signal for approaching a platform's memory ceiling before it actually triggers a low-memory condition. A router accepting the full internet routing table might show this gauge holding around several hundred megabytes; a sudden unexplained jump of tens of megabytes without a corresponding growth in route count would point to a CEF memory leak rather than normal route-table growth.