Explanation:

Default routing is a technique used in computer networking to route packets when no specific route is available in the routing table for the destination network. It is typically used in stub networks, which have only one exit path out of the network.

Stub Networks:
A stub network is a network that has only one exit path out of the network. It is often connected to a larger network, such as an Internet Service Provider (ISP), and does not have any other interconnected networks. Stub networks are usually used by small organizations or individual users who do not require complex routing capabilities.

Routing Table:
A routing table is a data structure stored in a router or a network device that contains information about the available routes to different networks. The routing table is used by the router to determine the next hop for forwarding packets to their destination.

Default Route:
A default route is a special route in the routing table that is used when no specific route is available for the destination network. It is often represented as 0.0.0.0/0, meaning that it matches all possible IP addresses. When a packet arrives at a router and there is no specific route for the destination network, the router will forward the packet using the default route.

Usage of Default Routing:
Default routing is commonly used in stub networks because they typically have only one exit path out of the network. In such networks, there is no need to maintain a complete routing table with specific routes for all possible destinations. Instead, a default route can be used to forward all packets that do not have a specific route.

Advantages of Default Routing:
- Simplifies the routing configuration: With default routing, there is no need to configure specific routes for all possible destinations. This simplifies the routing configuration and reduces the size of the routing table.
- Reduces network overhead: By using a default route, the router does not need to perform extensive route lookups for every packet. This reduces network overhead and improves the overall performance of the network.

Conclusion:
In conclusion, default routing is commonly used on stub networks, which have only one exit path out of the network. It simplifies the routing configuration and reduces network overhead. Other types of networks, such as those with multiple exit paths or a large number of exit paths, may require more complex routing protocols and strategies.