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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 learned by way of Type 1 and Type 2
LSAs.
- All routers then calculate the paths
to the other areas within the internetwork. These paths are learned
by way of interarea route entries, or Type 3 and Type 4 LSAs. If a
router has an interarea 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 any of the stub area types, 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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