EIGRP: ip default-network

mzinz

I'm having some trouble understanding what this command actually accomplishes.

It seems like it is similar to having a static route, except it is advertised.

Is this just a way to advertise a static route, so it benefits all routers in the AS, not just a single one?

NightShade1

Its what you said
ip default network advertise the other routers that he has a default route
If you simulate it you will see this default route with a * on it as a candidate for a default route

IF you did a static default route instead with ip route 0.0.0.0 0.0.0.0 command then he will be the only one knowing about that default route.

Check this maybe this helps
http://www.cisco.com/warp/public/105/default.html

mzinz

Oh,
So it's a way to advertise a default gateway? I thought it was just a way to automatically advertise any given route.

NightShade1

it just advertise how to get to that default route something like R* 192.168.2.0 via 172.16.1.1
when you see a * thats a potential default route
This is what the default network do it advertise that route so everyone knows that in that router there is a default route and they can sent unknown package to that router to route it to that network i think

marlon23

With "ip default-network" command, you will tell the router which network in routing table should be marked as default route (network must be reachable by router). This command will generate a static route for that network too (automatically), so it will be marked as S* in routing table of that router, and D* on another routers after redistribution - origin router will mark this route as default in updates. One important thing is that you need "no ip route" command to remove this default route and not "no ip defaul-network" from router.

You can also use "ip route 0.0.0.0 0.0.0.0 interface - not IP" but you need to add "network 0.0.0.0" config-router subcommand to redistribute this one.

cisco_trouble

is it not possible to redistribute a static route into the routing table in order to advertise it?