Where should we use default routing?

Default routing, often used in IP networking, is a simple but essential concept in routing management. It’s used when there isn’t a specific route defined for a destination in the routing table. Below are applications and scenarios where default routing should be used:

1. Small Networks: In small networks where there’s a single gateway to access external networks, default routing simplifies the configuration by directing all outbound traffic to that single gateway without the need for specific routes.

2. Stub Networks: A stub network has only one connection to a neighbor network. Since there’s only one way out, all traffic not destined for the local network can be sent to that single connection, making specific routes unnecessary.

3. Backup Routes: Default routing could be used as a fallback or backup route, directing traffic towards a secondary path if the primary path fails, assuming all other more specific routes are unavailable or down.

4. Internet Access from Enterprise Networks: In corporate or enterprise networks, where there might be complex internal routing but a single point of egress to the wider internet, default routing directs all external traffic to an internet gateway or firewall.

5. Simplifying Router Configuration: In routers connecting a local area network (LAN) to an internet service provider (ISP), default routing can simplify the configuration. Instead of maintaining a detailed list of routes for internet destinations, a default route sends all external traffic to the ISP.

6. VPN and Overlay Networks: Default routing can be useful in VPN scenarios