ip default-gateway vs. ip default-network
The ip default-network command can be used to inject a default route into your routing process.
If the router has an interface directly connected to the network specified with this command, the router will generate a default route and send that route to its neighbor routers.
This command can be a little tricky to use, and it works differently with different protocols. It’s easy to get ip default-network and ip default-gateway mixed up.
They’re both used to generate a default route. The key difference is that ip default-gateway is used when IP routing is off, while ip default-network is used when IP routing is on.