What does a router consult to determine the next hop for a destination IP packet?

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The router decides where to send a packet by consulting its routing table. It compares the destination IP address to the network prefixes in the table and uses the longest prefix match to pick the most specific route. The chosen entry provides the next-hop IP address or the exit interface to forward the packet toward its destination. If the destination is on a directly connected network, the routing decision still comes from the routing table, with the next hop effectively being the local next-hop on that network. After a next hop is selected, the router uses ARP to map that next-hop IP to a MAC address on the local link, which is a separate step from choosing the route. The ARP cache, NAT tables, and MAC address tables serve other purposes: ARP resolves local-layer addresses once the path is known, NAT translates addresses as packets traverse NAT devices, and MAC address tables help switches forward frames on a local network, not determine inter-network routes.