How does a router determine the next hop for a packet?

A router determines the next hop for a packet primarily by matching the destination IP address with its routing table. The routing table contains information about various network paths and the associated next hop addresses. When a packet arrives at the router, the router examines the destination IP address of that packet and searches its routing table for the best match. The routing table employs various algorithms and metrics to determine which path to use, ensuring efficient and effective packet forwarding towards its destination.

This process enables dynamic routing, as the router can adjust to network changes like rerouting around failures or taking advantage of less congested paths. The decision-making is not random nor solely based on manual configurations but relies heavily on this systematic lookup against a database of routes. This hierarchical approach helps large networks efficiently handle traffic and optimize routing decisions based on current topology and conditions.

Other factors like port numbers and MAC addresses may play roles in different layers of networking (such as Layer 2 for MAC addressing), but they are not directly involved in the routing decision process at Layer 3, where IP addresses are the focus. Moreover, while a manual entry could be part of configuring static routes, the dynamic nature of how most networking environments operate depends on the automated process of looking up routing tables.