Routing is the process of selecting the optimal path for data to travel from one network device to another. There are two main methods of routing: static and dynamic.
Static routing is a manual process where an administrator manually configures the routing table on each network device. Each route is entered into the table with a destination address and the exit interface or next-hop address to reach that destination. Once configured, the network device will always use that specific route until it is manually changed.
Dynamic routing, on the other hand, is an automatic process where a routing protocol is used to exchange information between network devices about available routes. The routing protocol will analyze the information, calculate the best path, and update the routing table accordingly. This type of routing is used in larger networks where the number of possible routes is large and changes frequently.
There are several advantages and disadvantages to each type of routing.
Static routing is relatively simple to configure and has low overhead, but it can be difficult to manage in larger networks since routes need to be manually configured on every network device. It also cannot adapt to changes in the network, such as device or link failures, without manual intervention. Static routing is generally best used in smaller networks with a limited number of routes that do not change frequently, such as in a small office or home network.
Dynamic routing, on the other hand, is more complex to configure and has higher overhead due to the routing protocol, but it can adapt to changes in the network automatically, making it ideal for large networks with a high number of routes that change frequently. Dynamic routing protocols can also support load balancing across multiple paths, providing redundancy in case of device or link failures, and can support advanced features such as route summarization, filtering and redistribution.
For example, in a small office network with only a few devices, static routing may be the best option since there are few routes and they are unlikely to change frequently. However, in a large enterprise network with multiple sites, hundreds of devices and multiple paths to reach different destinations, dynamic routing protocols such as OSPF or BGP would be a better choice since it can adapt to changes automatically, providing optimal paths to reach destinations reducing administrate overhead.