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Cyclades-PR1000
Chapter 9 - Routing Protocols 69
First, some definitions:
• An Autonomous System (AS) is a portion of the network that will use a single routing strategy. It is made up
of a backbone area and optionally of non-backbone areas.
• OSPF Areas are sub-systems that have identical routing databases. An area generally has no knowledge of
the routing databases of other areas.
• The Backbone connects areas and contains any routers not contained in another area.
• An Area Border Router connects areas and contains a separate database for each area it is contained in.
• An Autonomous System Boundary Router (ASBR) connects Autonomous Systems. The other Autonomous
System does not necessarily need to use OSPF.
STEP ONE
If using OSPF for the first time, sketch the network and determine which routers will make up the backbone and
each area. Determine if each router is an area border router or an autonomous system boundary router.