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OSPF: A Network Routing Protocol by Phani Raj Tadimety

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CHAPTER 9

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“Hello” Greetings from a Router

Mine’s Bond, James Bond.

—Ian Fleming, Casino Royale

Routers are social devices. They periodically broadcast a big “Hello” on their interfaces, hoping to receive positive responses. Likewise, they eagerly await similar “Hello” messages that might be broadcasted by neighboring routers.

Hello Message

Their “Hello” message is part of a (sub)protocol in OSPF, the Open Shortest Path First protocol discussed in Chapter 8. This is how a router fulfils its responsibility for dynamic discovery of neighboring router(s) on each of its interfaces. This messaging is the subject of this chapter.

The “Hello” message ...

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