RIP/RIPv2 advertising default route

[Jthnusmc]

This is just a personal curiosity.

When I configure RIPv2 on my router and I wanted to share the default route out, I did this command:

Router(config-router)# network 0.0.0.0

after this, I looked at the routing table in my router and the default route information is being shared.

HOWEVER, when I delete the previous command and did this command:

Router(config-router)# default-information originate

It's also sharing the default route information, shown in the routing table.

My question is: what's the difference between these two?

[Leonid Voronkin]

I think you do something wrong. Because command network does not advertise network specified in this command. It is said "advertise networks from interfaces which are in range specified in network command". And it is advertises only networks which belongs to the router interfaces. So command network 0.0.0.0 advertises all networks belonging to the router through all interfaces. But does not advertise default route.

[Cristian Matei]

Hi,

   In IGP's, the network statement is used to enable the protocol on specific interfaces and also bring those interfaces primary subnets into the protocol internal database in order to be advertised further. A network statement of "network 0.0.0.0" means match on everything. In distance vector protocols, like RIP and EIGRP (though EIGRP is known as "hybrid", fundamentally it is still distance vector), a network statement actually matches on connected routes, which means both connected as a result of having a subnet configured on the interface and connected as a result of  static route which has the egress interface specified (with or without next-hop information). So, "network 0.0.0.0" will make the routers advertise via RIP the default route, if it matches on a default route as connected, which it happens if you have a route configured such as "ip route 0.0.0.0 0.0.0.0 Fa0/0 10.10.10.1".

    The "default-information originate" tells RIP to advertise a default route unconditionally, and this its he method that should be used to advertise a default route via RIP.

Regards,

Cristian Matei.