Configuring OSPF stub areas
A stub area does not receive advertisements for external routes (AS-external LSAs, type 5) from an Area Border Router, which reduces the size of the link state database. Instead, routing to external destinations from within a stub area is based simply on the default route originated by a stub area border router. A stub area has only one area border router. Any packets destined outside the area are simply routed to that area border exit point where the packets are examined by the area border router and forwarded to a destination. ASBR's cannot be supported within a stub area. Without AS-external LSA's, stub area's cannot support virtual links.
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