What is the difference between the ip default-gateway, ip default-network, and ip route 0.0.0.0/0 commands?
The ip default-gateway command is used when IP routing is disabled on the router. However, ip default-network and ip route 0.0.0.0/0 are effective when IP routing is enabled on the router and they are used to route any packets which do not have an exact route match in the routing table. Refer to Configuring a Gateway of Last Resort Using IP Command for more information.