OSPF, default route

[matt_ccna]

Hi,

I have a question about OSPF, default route distribution and the network statements.

This is an exercises from my CCNA class, see attach for the setup.

Between ISP and Router A1 we have to use a static route, default route => ISP.
Network A1 - A2 - A3 - A2.1 => OSPF

If I configure OSPF on Router A1, do I have to add the network between A1 and ISP into the OSPF network statements of A1? Because the default route from A1 to ISP has been propagated from A1 to the other routers A2 - A3 - A2.1 (default-information originate).

The network works if I use both configurations, the only difference I see is the extra line in their routing table of the network A1 & ISP.

Which method is the right one and why?

Thx.

[cadet alain]

Hi,

use default-information originate  on the OSPF border router and do not put a network command encompassing the link to ISP. Why would you want to do this in this case?

Regards.

Alain

[JohnTylerPearce]

Cadet is right. You can include the network from A1 to ISP but there is no point. If any of your others routers don't have a specific match they will be default use the default route if one is configured. If you advertise the network range from A1 to ISP, for ANY traffic to match that, they will have to be looking for a route specific to that network.

[matt_ccna]

Ok, I got it now.

Thx a lot guys.