“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.
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 ...