Sunday, April 1, 2012

Solution -> OSPF AREA Challenge - A Little Tricky Stuff

Two months back I posted "OSPF Area Challenge" - Which so far only one person was able to solve - Siddharth Bhatia -

Siddharth is a Dual CCIE in both R&S & Sec Tracks.

Now lets talk about solution indeed. The solution was actually simple one. If you look closely at the diagram & requirement you basically see multiple OSPF Area 0 islands separated by other areas. Now for lack of better term, lots of time you will see this called as "Dis-contiguous Area 0". Now technically it's only Area 0 which can not be dis-contiguous, but any other area can be dis-contiguous and there is absolutely no problem about it at all.

Now to connect these OSPF Area 0 islands we can use Virtual Links. But there is another hidden problem introduced in Area 34 by configuring it as stub area. By default Stub area doesn't allow you to run virtual links. Or if you have configured virtual links across area and later configure it as "Stub". The virtual link eventually will get break. Solution to this problem - Configure Tunnel and Run virtual link inside the tunnel.

Lets see how topology will look like now :

so lets review configurations now:

Further Readings :

Deepak Arora

1 comment:

Anonymous said...

Deepak can you explain in detail why there is a need of backbone area in OSPF? the need of an area is to stop flooding of LSAs etc. then why are Area0? we already have areas.