Static routes are the routes we manually add to the routing table. Dynamic routes are the routes the router learns from routing protocols.
Routers use the routing table to make forwarding decisions. When a router receives a data packet, it compares the data packet's destination address with the destination addresses of all route entries available in the routing table.
- If it finds a match, it uses the interface specified in the entry to forward the data packet.
- If it finds multiple matches, it uses the interface specified in the entry matching the maximum IP bits to forward the data packet.
- If it does not find a match, it discards the data packet.
Since a router depends on routing table entries to make forwarding decisions, its routing table must contain entries before it can forward any data packet. A router with an empty routing table discards all packets. There are three ways to add routing entries to the routing table: automatic, static, and dynamic.
In the automatic method, the router automatically adds routing entries to the routing table based on the IP configurations we make on interfaces.
In the static method, we manually add routing entries to the routing table. Routers use the letter S to indicate the static routes in the routing table.
In the dynamic method, we configure a routing protocol, and that protocol automatically adds route information to the routing table. The routes a routing protocol adds to the routing table are known as dynamic routes. Routers use the routing protocol's identification letter to indicate dynamically learned routes in the routing table. For example, RIP is a routing table. Its identification letter is R. If we configure it on a router and it adds routes to the routing table, the router will use the letter R to indicate all of its routes.
This tutorial is part of the tutorial series "Understanding route types in the routing table.". 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
We use the show IP route command to view the routing table's entries.
The following table compares the static and manual methods.
| Manual method | Dynamic method |
| We manually add routing information to the routing table. The routes we manually add to the routing table are known as static, floating static, and default routes. | We configure a routing protocol on all routers of the network. The routing protocol automatically discovers all network routes and adds them to the routing table. |
| The default AD value of a static route is 1. | The AD value of a dynamic route depends on its source routing protocol. Different routing protocols have different AD values. |
| Routers do not manage these routes. We have to manage them manually. For example, if a route goes down, we have to manually remove it from the routing table. | Routing protocols manage these routes. If a route goes down, the routing protocol automatically removes it from the routing table. |
| It is easy to configure but hard to manage. | It is hard to configure but easy to manage. |
