CCNA 3 Labs and Study Guide - BINARYBB.INFO – @jagalbraith

102 Switching Basics and Intermediate Routing CCNA 3 Labs and Study Guide
Concept Questions
What two names refer to the same algorithm used by all link-state routing protocols?
Link-state routing protocols were made possible by the algorithm formulated by Edsger Wybe Dijkstra.
Thus, it is called the Dijkstra algorithm. More generically, it is called the Shortest Path First algorithm. For
more on Dijkstra, visit Wikipedia at http://en.wikipedia.org/wiki/Edsger Dijkstra.
What is the difference between the way link-state routing protocols view the network and the way distance
vector routing protocols view the network?
Link-state routing protocols build a tree-like structure of the network, with the local router as the root of
the tree. Each link-state router has knowledge of the entire network. Link-state routers do not depend on
other routers to advertise the best route. Link-state routers calculate an algorithm to determine the best
route to the destination. Distance vector routing has also been called “routing by rumor” and “gossip routing.”
Distance vector routers depend upon directly connected neighbors to advertise the best route to the
destination.
Journal Entry
Describe a network implementation where a distance vector routing protocol would be preferred over a
link-state routing protocol.
First, the current networking devices may not support link-state routing, and the budget for the implementation
may not be sufficient to purchase additional equipment.
Second, the network may be simple enough that the benefits of a link-state routing protocol is overkill. For
example, a network with only a handful of subnets, a few routers and servers, and only one gateway would
not normally need the features of a link-state routing protocol. In fact, you may not want to run a routing
protocol at all. Instead, you may want to use static routes.
Finally, the network administration of the network may not have the necessary training and skills to implement
and monitor a link-state routing protocol, which can be more complex than distance vector routing or
static routing.
Single-Area OSPF Concepts
One of the main limitations of OSPF is its sheer complexity. Although you are only responsible for understanding
single-area OSPF concepts and configurations, it is still the most complex routing protocol you
will use at the CCNA level. The exercises in the section focus on the conceptual framework of OSPF. It is
important to have a good grasp of these concepts before proceeding into the configuration of OSPF. The
following exercises build on each other and are best done in sequence.
Vocabulary Exercise: Completion
Complete the paragraphs that follow by filling in appropriate words and phrases.
OSPF is a routing protocol developed for IP networks by the OSPF working group of the Internet
Engineering Task Force (IETF). OSPF has two primary characteristics. The first is that the protocol is an
open standard, which means that its specification is in the public domain, described in RFC 2328. The second
principal characteristic is that OSPF is based on the Dijkstra or SPF algorithm.
OSPF is a link-state routing protocol, whereas RIP and IGRP are distance vector routing protocols.
Routers that are running distance vector algorithms send all or a portion of their routing tables in routingupdate
messages to their neighbors.