Which routing table stores IPv4 unicast routes and is used by multicast routing protocols to prevent loops?

`inet.0` is the primary IPv4 unicast routing table but is not directly used by multicast protocols for RPF loop prevention.

`inet.1` is the multicast forwarding cache (forwarding information base), which contains entries for actual multicast forwarding, not for RPF loop prevention by routing protocols.

The `inet.2` routing table is dedicated to storing unicast routes that multicast routing protocols, such as PIM, use to perform RPF checks, ensuring that multicast traffic originates from a valid path and preventing loops. Multicast protocols consult `inet.2` to verify the path back to a multicast source.

`inet.3` is used for MPLS path information and is not involved in IPv4 unicast routing for multicast RPF checks.