CCNA Exploration Module 2 Chapter 3Introduction to Dynamic Routing Protocols

V 4.0

3.1.1 What are the four routing protocols that are the focus of this course?

Routing Information Protocol (RIP), Open ShortestPath First (OSPF), Enhanced IGRP (EIGRP),Boarder Gateway Routing (BGP)101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.1.1.2 What are routing protocols? Used to facilitate the exchange of routinginformation between routers. They allow routers todynamically share information about remotenetworks and automatically add this information totheir own routing tables.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is one of the primary benefits of using a dynamic routing protocol?

Routers exchange routing information wheneverthere is a topology change. This exchange allowsrouters to automatically learn about new networksand also to find alternate paths when there is a linkfalure to a current network.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Do dynamic routing protocols 1Less01010101010101101010

require more or less administrative overhead as compared to static routing?

001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110

111101010101010001100What is he expense of using dynamic routing protocols?

Dedicating part of a router's resources for protocoloperation including CPU time and network linkbandwith.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.1.2.1 A set of processes, algorithms, and messages that are used to exchange routing information and populate the routing table with the routing protocol's choice of best paths is the definition of what networking process?

Routing protocol101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the purposes of a routing protocol?

Discovery of remote networksMaintaining up-to-date routing informationChoosing the best path to destination networksAbility to find a new best path if the current path isno longer available101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

List and define the three components of routing protocols?

Data structures - Some routing protocols use tablesand/or databases for its operations. This informationis kept in RAM.Algorithm - An algorithm is a finite list of steps usedin accomplishing a task. Routing protocols

usealgorithms for facilitating routing information and forbest path determination.Routing protocol messages - Routing protocols usevarious types of messages to discover neighboringrouters, exchange routing information, and othertasks to learn and maintain accurate informationabout the network.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the four general operations of a dynamic routing protocol?

The router sends and receives routing messages onits interfaces.The router shares routing messages and routinginformation with other routers that are using thesame routing protocol.Routers exchange routing information to learn aboutremote networks.When a router detects a topology change therouting protocol can advertise this change to otherrouters.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.1.3.1 What are the primary uses for static routing?

Providing ease of routing table maintenance insmaller networks that are not expected to growsignificantly.Routing to and from stub networks (see

Chapter 2).Use of a single default route, used to represent apath to any network that does not have a morespecific match with another route in the routingtable.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the advantages of static routing?

1Minimal CPU processing.Easier for administrator to understand.Easy to configure.0101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are disadvantages of static routing?

Configuration and maintenance is time-consuming.Configuration is error-prone, especially in largenetworks.Administrator intervention is required to maintainchanging route information.Does not scale well with growing networks;maintenance becomes cumbersome.Requires complete knowledge of the whole networkfor proper implementation.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the advantages of dynamic routing?

Administrator has less work maintaining theconfiguration when adding or deleting networks.

Protocols automatically react to the topologychanges.Configuration is less error-prone.More scalable, growing the network usually doesnot present a problem.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the disadvantages of dynamic routing?

Router resources are used (CPU cycles, memoryand link bandwidth).More administrator knowledge is required forconfiguration, verification, and troubleshooting.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.2.1 What are the distance vector protocols?

RIP, IGRP, EIGRP (counts hops)101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the link state protocols?

OSPF, IS-IS101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the exterior routing protocol listed?

BGP101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110

1111010101010100011003.2.2 What is an Autonomous

System?otherwise known as a routing domain - is acollection of routers under a commonadministration.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is another name for an Autonomous System?

routing domain101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are Interior Gateway Protocols used for?

are used for intra-autonomous system routing -routing inside an autonomous system.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are Exterior Gateway Protocols used for?

are used for inter-autonomous system routing -routing between autonomous systems.

1010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.2.3 What are the two classifications of IGP’s?

Distance vector routing protocolsLink-state routing protocols101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010

101010011111111010101010100101111110011110111101010101010001100

What is a vector? routes are advertised as vectors of distance anddirection. Distance vector protocols typically usethe Bellman-Ford algorithm for the best path routedetermination.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Define distance and direction. Distance is defined in terms of a metric such as hopcount and direction is simply the next-hop router orexit interface.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Where does a distance vector router receive its information from?

Some distance vector protocols periodically sendcomplete routing tables to all connected neighbors.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Do distance vector protocols have a map of the entire network?

Distance vector protocols use routers as sign postsalong the path to the final destination. The onlyinformation a router knows about a remote networkis the distance or metric to reach that network andwhich path or interface to use to get there.

Distancevector routing protocols do not have an actual mapof the network topology.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Where do distance vector protocols work best?

The network is simple and flat and does not requirea special hierarchical design.The administrators do not have enough knowledgeto configure and troubleshoot link-state protocols.Specific types of networks, such as hub-and-spokenetworks, are being implemented.Worst-case convergence times in a network are nota concern.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.2.3.2 What can a link-state router do that a link state router can not?

a router configured with a link-state routing protocol can create a "complete view" or topology of the network by gathering information from all of the other routers.Link-state routing protocols do not use periodic updates.0101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Define converged. When the intermediate devices all have the sameconsistant network topology in their routing tables101010101010101101010001111101001010101010

110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

When are updates sent in a link-state network?

Some distance vector protocols periodically sendcomplete routing tables to all connected neighbors.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the best situations to use a link-state protocol?

The network design is hierarchical, usually occurringin large networks.The administrators have a good knowledge of theimplemented link-state routing protocol.Fast convergence of the network is crucial.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.2.4 What do classful routing protocols not send in their updates?

subnet mask information in routing updates.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the situation where you can not use a classful routing protocol?

Classful routing protocols cannot be used when anetwork is subnetted using more than one subnetmask, in other words classful routing protocols do not support variable length subnet masks (VLSM).101010101010101101010001111101001010101010110110101010110101001

010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the two classful routing protocols?

RIPv1 and IGRP.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What do classless routing protocols include in their updates?

Classless routing protocols include the subnet maskwith the network address in routing updates.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What are the classless routing protocols?

RIPv2, EIGRP, OSPF, IS-IS, BGP101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.2.5 Define convergence? Convergence is when all routers' routing tables areat a state of consistency. The network hasconverged when all routers have complete andaccurate information about the network.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is convergence time? Convergence time is the time it takes routers toshare information, calculate best paths, and

updatetheir routing tables. A network is not completelyoperable until the network has converged; therefore,most networks require short convergence times.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Which 2 protocols are slow to converge?

RIP and IGRP101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Which 2 protocols are faster to converge?

EIGRP and OSPF101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.3.1 What is a metric? A metric is a value used by routing protocols toassign costs to reach remote networks.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the metric used for? he metric is used to determine which path is mostpreferable when there are multiple paths to thesame remote network.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010

101010011111111010101010100101111110011110111101010101010001100

What is the metric for RIP? hop count101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the metric for EIGRP? combination of bandwidth and delay101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the metric for OSPF? bandwidth101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What does hop count refer to? the number of routers a packet must cross to reachthe destination network101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.3.2 Can metrics from one routing protocol be compared to another routing protocol’s metric?

The metric used by one routing protocol is notcomparable to the metric used by another routingprotocol. Two different routing protocols mightchoose different paths to the same destination dueto using different metrics.101010101010101101010001111101001010101010

110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

List and define the possible metrics to choose from?

Hop count - A simple metric that counts the numberof routers a packet must traverseBandwidth - Influences path selection by preferringthe path with the highest bandwidthLoad - Considers the traffic utilization of a certainlinkDelay - Considers the time a packet takes totraverse a pathReliability - Assesses the probability of a link failure,calculated from the interface error count or previouslink failuresCost - A value determined either by the IOS or bythe network administrator to indicate preference for a route. Cost can represent a metric, a combinationof metrics or a policy.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.3.2.2 List and explain each routing protocol and the metric it uses.

RIP: Hop count - Best path is chosen by the routewith the lowest hop count.IGRP and EIGRP: Bandwidth, Delay, Reliability, andLoad - Best path is chosen by the route with thesmallest composite metric value calculated fromthese multiple parameters. By default, onlybandwidth and delay are used.IS-IS and OSPF: Cost - Best path is chosen by theroute with the lowest cost. . Cisco's

implementationof OSPF uses bandwidth. IS-IS is discussed inCCNP.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

In the show ip route display where is the metric listed?

The metric associated with a certain route can bebest viewed using the show ip route command. Themetric value is the second value in the brackets fora routing table entry.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.3.3 What is the process used to forward packets when 2 or more paths have equal costs?

Instead, the router "load balances" between theseequal cost paths. The packets are forwarded usingall equal-cost paths.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

Where can you look to determine if load balancing is being used?

Load balancing is in effect if two or more routes areassociated with the same destination101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.4.1 What are the possible values for Administrative Distance?

an integer value from 0 to 255101010101010101101010001111101001010101010

110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What is the best value for administrative distance?

0101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What type of route has the lowest possible administrative distance?

directly connected network101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What does an administrative distance of 255 mean?

the router will not believe the source of that routeand it will not be installed in the routing table101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.4.1.2 Where can you find the administrative distance in the show ip route output?

The AD value is the first value in the brackets for arouting table entry.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

How does a router choose the best path if two routing protocols are being used?

Lowest AD101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101

010100101111110011110111101010101010001100

What are the two commands in which you can determine what the administrative distance is?

Show ip routeShow ip rip database101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.4.3 What is the administrative distance for a static route?

1101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

If you configure a route to a destination also learned by a dynamic routing protocol, what would you set the administrative distance to?

The static route will be configured with an ADgreater than that of the routing protocol. If there is alink failure in the path used by the dynamic routingprotocol, the route entered by the routing protocol isremoved from the routing table. The static route willthen become the only source and will automaticallybe added to the routing table. This is known as a floating static route and is discussed in CCNP.101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What command can be issued to see the AD of a specific route?

Show ip route101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.4.4 Can you change the AD of a directly connected route?

no101010101010101101010001111101001010101010

110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

What command can be issued to see the AD of a directly connected route?

Show ip route101010101010101101010001111101001010101010110110101010110101001010101011010101101010111111100101010101010101010011111111010101010100101111110011110111101010101010001100

3.5.1 This is excellent practice for the exam. These are easy questions to right and if you practice they are easy to answer.