OSPF forces a 2-tier hierarchy design with the backbone area requirment. It was designed this way to allow the protocol to scale better than a flat topology such as EIGRP. Your areas limit the LSA flooding scope and the backbone area uses Type 3 summary to flood inter-area routes in a single LSA. The area requirement is for scaling and is not a loop prevention mechanism in itself. Sent wirelessly from my BlackBerry device on the Bell network.
-----Original Message----- From: Chidhu R <[email protected]> Sender: [email protected] Date: Tue, 31 Jul 2012 12:47:33 To: <[email protected]> Subject: [OSL | CCIE_RS] Fwd: OSPF Backbone area rule I am aware of the basic facts and that inter area connection is a distance vector logic. It would be greatly helpful if you can provide me an example of how a loop will form when this condition is violated. Thanks Chid ---------- Forwarded message ---------- From: Chidhu R <[email protected]> Date: Tue, Jul 31, 2012 at 12:27 PM Subject: OSPF Backbone area rule To: [email protected] Hi, Can someone explain me, in OSPF, - Why every area must be connected to area 0 and why those routes in areas which are not connected to area 0 are not being redistributed across the OSPF domain. ( which led virtual link concept i suppose ) - Why any router which is an ABR should be connected to area 0 and why a router which is not connected to area 0 but connected to multiple areas do not summarize the type 3 LSAs. Also please explain one more doubt in the picture attached with this thread. When checked in R5, i am able to see all the routes including the route between R1 and R2 ( *this is not connected to area 0, yet i am able to see the routes and there is no Virtual link configured )* Thanks Chid _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
