OSPF Areas

When you start with OSPF, everything seems to be simple. But later on you learn about many differnent types of OSPF areas.

  • Stub area – has no connection to external networks, it does not contain any external routes, relieys mostly on default routes, does not have AS-external routes (Type 5 LSAs)
  • Totaly Stub area – is an extension to the stub area and includes external routes and routes to other area over a default route, get these by Typ 3LSAs, does not support summary routes
  • Backbone area – is always area zero
  • NSSA, Not so stubby area – the same as SA, but can import external routes and send them to the backbone or other areas, type 3 and type 4 summary routes are not advertised into NSSA



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