Routing table
A router's lookup table — for each destination prefix, which interface/next-hop the packet should be sent to. Uses longest prefix match to pick the most specific rule.
Two tables per router: RIB (Routing Information Base — all routes from BGP/OSPF/static), FIB (Forwarding Information Base — the actual table hardware consults per packet, often in TCAM). A full internet routing table is ~970,000 IPv4 prefixes + ~200,000 IPv6 prefixes (June 2024). Routers without enough TCAM have to drop routes or fall back to a default route (0.0.0.0/0). Commands: ip route (Linux), show ip route (Cisco).