In large networks, how do most routers obtain their routing tables?

Most routers obtain their routing tables by automatically building and maintaining them through protocols known as dynamic routing protocols. These protocols, such as OSPF, EIGRP, and BGP, enable routers to communicate with each other and exchange information about network topology and reachable networks. As a result, each router gathers information about the network and dynamically updates its routing table, ensuring that it can route packets efficiently according to the most current network conditions.

This automatic building and maintenance process allows routers to adapt to network changes, such as the addition or removal of devices or links, without requiring manual intervention by a network administrator. This feature is essential in large networks where manual configuration would be time-consuming and prone to errors, making dynamic routing the preferred method for efficient network management.