Routing table updating methods

Routers use routing table entries to make forwarding decisions. There are three ways to update the routing table entries: automatic, manual, and dynamic.

In the automatic method, the router automatically adds routing information to the routing table from the IP configuration you assign to its interfaces. The routes the router adds from the IP configuration of interfaces are called the directly connected and local routes. It uses the directly connected routes to reach the network connected to the interface. It uses the local route to reach the interface.

In the manual method, you manually add routing information to the routing table. The routes you manually add to the routing table are known as static, floating static, and default routes.

In the dynamic method, you configure a routing protocol on all routers in the network. The routing protocol automatically discovers all routes from the network and adds them to each router's routing table.

The following table compares all three routing methods.

Parameter	Automatic	Manual	Dynamic
Speed	It is a fast method. The router adds the routes to the routing table as soon as you start the interface with the IP configuration.	It is a typical method. The router adds the route to the routing table when you configure it.	It is a slow method. The router depends on the routing protocols. Different routing protocols take different amounts of time to discover network routes.
Configuration	The router automatically learns the routes from the IP configuration you assign to the interfaces. You do not need to change any additional settings for it.	The router learns the routes from the configuration you make in global configuration mode.	The router learns the routes from the routing protocol you configure.
Update	The router automatically updates these routes when you update the IP configuration on interfaces.	To update these routes in the routing table, you must manually modify the corresponding routes in global configuration mode.	The routing protocol updates the routing table with these routes.
Remove	The router automatically removes these routes when you shut down the related interfaces.	To remove these routes from the routing table, you must manually delete the corresponding routes in global configuration mode.	If any route goes down, the routing protocol removes it from the routing table.
Management	The management is simple.	The management is moderate.	The management is complex.

This tutorial is part of the tutorial series "Routing Table Updating Methods and Route Types". Other parts of this series are the following.
Chapter 1  The show IP route command on Routers
Chapter 2  Routing Table Updating Methods
Chapter 3  Directly Connected Routes and Local Routes
Chapter 4  Static and Floating Static Routes Explained
Chapter 5  Static and Dynamic routes in the Routing table
Chapter 6  Default Route in the Routing Table
Chapter 7  Network Routes and Host Routes Explained
Chapter 8  CCNA Exam Practice Question with Answer 1

Key points:-

Routers use the routing table to make forwarding decisions.
There are three ways to add entries to the routing table.
In the automatic method, the router learns routes from the IP configurations you set on the interfaces.
In the manual method, you manually add routes to the routing table.
In the dynamic method, you configure a routing protocol that learns, adds, and manages all network routes.

By ComputerNetworkingNotes Updated on 2025-12-08