FIB compression is enabled for IPv4 and IPv6, supporting up to (approximately) 5.7 M IPv4 routes and 900 K IPv6 routes. Refer to release notes and scale documentation for further information.
Note the following:
FIB next-hop/adjacency comprises the set of IGP paths used for forwarding a packet, for example, ECMP paths used by a route to forward matching packets.
If both a less-specific route and a more-specific route point to the same next-hop/adjacency, the more-specific route is not programmed in hardware.
The packet for the less-specific route hits the parent route with the same next-hop, ensuring that there is no traffic black hole, and forwarding result is the same.
Because compression requires a parent route with the same next-hop, Level 1 routes cannot be compressed, as they may not have a parent route (default route).
Level 1 routes in the Internet BGP FIB can be compressed in the range of 40% to 50%.