Understanding OSPF Design

Understanding OSPF Core design 

 Charter 18

 Before everything we need to understand 3 things: 

1. Why OSPF Areas

   OSPF Routers Type (ABR and ASBR)

   OSPF virtual links 

 

 

All routers have 3 tables :

 The larger that  an area gets, the least efficient it gets

Areas boundaries give the opportunities  for summarization, (ABR)  Areas Border Routes  makes everything more efficient

The autonomous system Boundaries routes (ASBR) reach outside world into OSPF.It could be internet or another protocol.

An ASBR can summarize between two different  protocol types

As a general rules, all areas must connect to area 0

For a long distance location, you can have a virtual link.You might make it think it's another Area 0, or an area 3.

You might want to bend the rules and makes it believe its  a tunnel or a VPN..a trick
Virtual link makes an outside area thinks they are virtually connected.