
Customizing OSPF Services
114065 Rev. A 5-31
Figure 5-6. Area Border Router
Each border router in an AS
• Receives routing information from its attached areas, creates summaries of
this information, and forwards the summaries to the backbone and to any
other attached area. In
Figure 5-6, for example, Border router 2 floods
summaries from Area B to the backbone and Area C. Through the backbone,
the summaries are forwarded to all other areas in the AS.
• Receives (via the backbone) summaries from other border routers, uses this
information to create new routing summaries (which add in the cost of the
backbone routes), and forwards the new summaries to its attached areas.
Backbone Network
Area B Network
Area A Network
Area C
Internal
Router
Area B
Internal
Router
Area A
Internal
Router
Border
Router 2
Border
Router 1
Area C Network
IP0002A
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