Hi @sachandio!
There are three types of instructions for specifying the default route (last resort gateway), which can be divided into two categories:
1. ip default-gateway
When the ip routing on the router is invalid, use it to specify the default route for installing IOS in RXBoot mode (no ip routing), etc. Or turn off ip routing and let the router be used as a host. At this time, you need to configure the default gateway.
2. ip default-network and ip route 0.0.0.0 0.0.0.0
Both are used on routers where ip routing is effective. The main difference lies in whether the routing protocol propagates this routing information. For example: IGRP cannot recognize 0.0.0.0, so ip default-network must be used when propagating the default route.
When using the ip default-network command to set multiple default routes, the one with the shortest administrative distance becomes the final default route; if there are multiple routes with the same distance value, the upper one in the routing table (show ip route) becomes the default route.
When both ip default-network and ip route 0.0.0.0 0.0.0.0 are used to set the default route at the same time, if the network set by ip default-network is directly connected (static and known), then it becomes the default route; if the network specified by ip default-network is obtained by exchanging routing information, the entry specified by ip route 0.0.0.0 0.0.0.0 becomes the default route.
Finally, if multiple ip route 0.0.0.0 0.0.0.0 instructions are used, the traffic will be automatically load balanced on multiple links.
