Which of the following statements about OSPF neighbor relationship establishment is false?

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The answer is D.
The OSPF authentication is not mandatory, so, the authentication modes on both ends of a link must be interface authentication, area authentication, or none-authenticatin.

O D. The authentication modes on both ends of a link must be interface authentication or area authentication.

OSPF is a link-state protocol based on the open standard. At a high level, OSPF operation consists of three main elements: neighbor discovery, link-state information exchange, and best-path calculation.

To calculate the best path, OSPF uses the shortest path first (SPF) or Dijkstra’s algorithm. The input information for SPF calculation is link-state information, which is exchanged between routers using several different OSPF message types. These message types help improve convergence and scalability in multi-area OSPF deployments.

OSPF also supports several different network types, which enables you to configure OSPF over a variety of different underlying network technologies.

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