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All routers wait five seconds and then run the shortest path first (SPF)
algorithm. After the algorithm is run, RouterD adds the route through
RouterE, and Routers C, B, and A update the metric in their routing
table to that route.
After another 30 seconds, RouterF sends an LSA out all interfaces
after timing out the link to RouterD. All routers wait five seconds and
then run the SPF algorithm, and all routers now know that the route
to the failed link is through RouterE.
RouterA convergence time is the time of detection, plus the LSA forward-
ing time, plus five seconds. This is about six seconds. However, if RouterF's
time to converge is considered, then the time is about 36 seconds.
his chapter described the difference between distance-vector and
link-state routing protocols. The idea of this chapter was to provide you with
an overview of the different types of routing protocols available, not how to
configure routers.
Both link-state and distance-vector routing algorithms were covered, as
well as how they create routing tables and regulate performance with timers,
and their different convergence methods.
The difference between classful and classless routing protocols is very
important to understand before continuing on with the other chapters in this
book. We discussed both types of routing protocols in detail.
Key Terms
Before taking the exam, make sure you're familiar with the following terms:
administrative distances
autonomous systems (AS)
composite metric
distance-vector protocol
dynamic routing
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