Area 0 was just decided back in the dim dark days of OSPF to be the "top" area. After all you cant get lower than zer0 so its a logical choice.
Loop prevention - there can only be one area 0, therefore it cant pass through it twice (unless you do some trickery with virtual-links) and loops cant occur Hierarchy - As above, Area 0 was decided to be the top. Its in the protocol. If you really feel like it then you can configure a single area OSPF instance with no area 0. I recall a client with a terribly designed network with everything in a single area 77 (the OSPF design was the least of this guys problems though). Design constraint - specified in the protocol. Its like saying when you design a car it has to have wheels. Unless your name is Marty McFly of course. Cheers, Matt CCIE #22386 CCSI #31207 On 5 January 2011 09:52, Sanjay Singh <[email protected]> wrote: > Hello ! > > Why area 0 is required in OSPF? > I have read multiple blogs but didn't find any satisfactory answer, some > says- > > + Area 0 implemented for loop prevention. if yes.. then a big HOW ?? > + Area 0 is implemented to allow a level of hierarchy and to allow OSPF and > to provide summarisation/filtering across area boundaries.. if yes.. then > Cann't we implement hierarchy or summarization without area 0 ??? > + Design constraint.. if yes.. then WHAT is the design constraint.. there > must be some logical reason behind it ???? > -- > Regards, > *Sanjay Singh* > Mob-9717775461 > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
