The steps for OSPF convergence are as follows:
Step 1 When a router detects a link failure, an LSA is sent to its neighbors. If the router is on a multiaccess link, then the update is sent to the DR and BDR, not to all neighbors.
Step 2 The path is removed from the originating router's tables.
Step 3 On receipt of the LSA, all routers update the topology table and flood the LSA out its interfaces.
Step 4 The Dijkstra algorithm is run to rebuild the routing table.
Convergence is detection time, plus LSA flooding, plus 5 seconds before computing the topology table. This comes to a few seconds. If convergence is deemed to be the topology table being updated, this could take longer.
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