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After all routers receive the routing
updates, they add them to their link-state databases and recalculate
their routing tables. The order in which paths are calculated is as
follows:
- All routers first calculate the paths to destinations within
their area and add these entries into the routing table. These are
the Type-1 and Type-2 LSAs.
- All routers then calculate the paths to the other areas
within the internetwork. These paths are the inter-area route
entries, or Type-3 and Type-4 LSAs. If a router has an inter-area
route to a destination and an intra-area route to the same
destination, the intra-area route is kept.
- All routers, except those that are in a form of stub area,
then calculate the paths to the AS external (Type-5) destinations.
At this point, a router can reach any network within or outside
the OSPF autonomous system.
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