What is difference between ip default-network vs ip route 0.0.0.0? Is lookup in routing tbl for one faster?

Question

ip default-network and ip rute 0.0.0.0 0.0.0.0 commands are set where ip routing is enabled. Both are static routes but seems to do the same. Maybe the lookup in a routing tbl for one is faster than the other, although I doubt.

Answer 1

you mean default route and ip 0.0.0.0?

both works the same. default route means, the ip network has default gateway to go to in case an ip address is not found. the same with ip 0.0.0.0, means for any destination other than stated as static routes, it will go to some gateway.

the fastest routing table will be static routing. i'm not sure how do you set up your routing table, but if you are using static routing, then most of the time, you will use the 0.0.0.0 function. if you do dynamic routing, then it doesn't matter. but mind you that in a small network, you won't feel that much different between static and dynamic routing, except if you have many VLANs, or different IP classes and subnets.

hope that helps

Answer 2

Without any dynamic protocols running, you can configure your router to choose from a number of candidate default routes based on whether the routing table has routes to networks other than 0.0.0.0/0. The ip default-network command allows you to configure robustness into the selection of a gateway of last resort. Rather than configuring static routes to specific next-hops, you can have the router choose a default route to a particular network by checking in the routing table.

The ip default-network command is classful. This means that if the router has a route to the subnet indicated by this command, it installs the route to the major net. At this point neither network has been flagged as the default network. The ip default-network command must be issued again, using the major net, in order to flag the candidate default route.