ip route 0.0.0.0 vs ip default-network

I don't understand how ip default-network works. My understanding of the ip route 0.0.0.0 command is it's basically a default gateway, or default route. This route sends any traffic that doesn't have a more specific route to the destination ip.

The reason that the ip default-network command confuses me is that you have to specify the network and the book im reading implies that these two commands are basically the same. So if I have the command "ip default-network 10.0.0.0", how could that route any traffic other than 10.0.0.0/8 traffic?

Am I looking too far into this or something?

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Comments

lon21

I was the same as you, both commands are the same.

With the IP route you would give a d/w and with the ip default you would use the network address, but when you do show ip route, if I can remember both will show with a default root.

Try it and let us know.

Your default route would be only a different ip address from your connected devices, thats how it picks it up.

Greenmet29

Hmmm.. thanks for the reply but i'm still confused. I'm going to have to lab it up tonight. After reading a little more in odem's icnd2 book, I understand a little bit better. It has someting to do with classful/classless ip routing.

Bl8ckr0uter

There is some difference. Check this link out:

https://learningnetwork.cisco.com/thread/23249

MrRyte

Here's my understanding of the subtle difference between the two:

The major difference between these two options is that configuring a static default route only defines a default route for the router you're configuring it on, while ip default-network will propagate the route via its routing protocol.

Taken from here:
Cisco CCNA CCNP Exam Training IP Default Network Command

tattoo_tech

One difference that comes to mind is in EIGRP. Say you have a quad zero static route out of your network as well as several other static routes. How do you propagate it into your network? "redistribute static" well the problem is that it will propogate all static routes, not just the quad zeros. So default network will propogate only the default route and not other statics you might have on the edge router. Its used more in multi area topologies and when redistributing one routing protocol into another.

TT

snokerpoker

Thanks for the link MrRyte!