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SEMESTER 2 Chapter 3 Introduction to Dynamic Routing Protocols V 4.0 3.1.1 3.1.1.2 What are the four routing protocols that are the focus of this course? What are routing protocols? What is one of the primary benefits of using a dynamic routing protocol? Do dynamic routing protocols require more or less administrative overhead as compared to static routing? What is he expense of using dynamic routing protocols? 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? What are the purposes of a routing protocol? List and define the three components of routing protocols? What are the four general operations of a dynamic routing protocol? RIP, RIPv2, EIGRP, OSPFv2 allow routers to dynamically share information about remote networks and automatically add this information to their own routing tables routers exchange routing information whenever there is a topology change Less dedicating part of a router's resources for protocol operation including CPU time and network link bandwidth Routing protocol Discovery of remote networks Maintaining up-to-date routing information Choosing the best path to destination networks Ability to find a new best path if the current path is no longer available Data structures - Some routing protocols use tables and/or databases for its operations. This information is kept in RAM, Algorithm- An algorithm is a finite list of steps used in accomplishing a task. Routing protocols use algorithms for facilitating routing information and for best path determination. Routing protocol messages - Routing protocols use various types of messages to discover neighboring routers, exchange routing information, and other tasks to learn and maintain accurate information about the network. The router sends and receives routing messages on its interfaces. The router shares routing messages and routing information with other routers that are using the 3.1.3.1 What are the primary uses for static routing? What are the advantages of static routing? What are disadvantages of static routing? What are the advantages of dynamic routing? What are the disadvantages of dynamic routing? 3.2.1 3.2.2 What are the distance vector protocols? What are the link state protocols? What is the exterior routing protocol listed? What is an Autonomous System? What is another name for an Autonomous System? What are Interior Gateway Protocols used for? What are Exterior Gateway same routing protocol. Routers exchange routing information to learn about remote networks. When a router detects a topology change the routing protocol can advertise this change to other routers. Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly. Routing to and from stub networks. Use of a single default route, used to represent a path to any network that does not have a more specific match with another route in the routing table. Minimal CPU processing. Easier for administrator to understand. Easy to configure. Configuration and maintenance is time-consuming. Configuration is error-prone, especially in large networks. Administrator intervention is required to maintain changing route information. Does not scale well with growing networks; maintenance becomes cumbersome. Requires complete knowledge of the whole network for proper implementation. Administrator has less work maintaining the configuration when adding or deleting networks. Protocols automatically react to the topology changes. Configuration is less error-prone. More scalable, growing the network usually does not present a problem. Router resources are used (CPU cycles, memory and link bandwidth). More administrator knowledge is required for configuration, verification, and troubleshooting. RIPv1, RIPv2, IGRP, EIGRP IS-IS, OSPF BGP a collection of routers under a common administration Domain intra-autonomous system routing - routing inside an autonomous system inter-autonomous system routing - routing between 3.2.3 Protocols used for? What are the two classifications of IGP’s? What is a vector? Define distance and direction. Where does a distance vector router receive its information from? Do distance vector protocols have a map of the entire network? Where do distance vector protocols work best? 3.2.3.2 What can a link-state router do that a link state router can not? Define converged. When are updates sent in a link-state network? What are the best situations to use a link-state protocol? 3.2.4 3.2.5 What do classful routing protocols not send in their updates? What is the situation where you can not use a classful routing protocol? What are the two classful routing protocols? What do classless routing protocols include in their updates? What are the classless routing protocols? Define convergence? What is convergence time? autonomous systems Distance vector routing protocols Link-state routing protocols distance and direction Distance is defined in terms of a metric such as hop count and direction is simply the next-hop router or exit interface From its neighbors No The network is simple and flat and does not require a special hierarchical design. The administrators do not have enough knowledge to configure and troubleshoot link-state protocols. Specific types of networks, such as hub-and-spoke networks, are being implemented. Worst-case convergence times in a network are not a concern. Get a complete view of the topology of the network When intermediate devices all have the same consistent network topology in their routing tables. Only when the topology changes The network design is hierarchical, usually occurring in large networks. The administrators have a good knowledge of the implemented link-state routing protocol. Fast convergence of the network is crucial. Subnet masks When you use different subnet masks RIP and IGRP Subnet mask RIPv2, EIGRP, OSPF, IS-IS, BGP when all routers' routing tables are at a state of consistency the time it takes routers to share information, calculate best paths, and update their routing tables 3.3.1 Which 2 protocols are slow to converge? Which 2 protocols are faster to converge? What is a metric? What is the metric used for? What is the metric for RIP? What is the metric for EIGRP? What is the metric for OSPF? What does hop count refer to? 3.3.2 3.3.2.2 3.3.3 Can metrics from one routing protocol be compared to another routing protocol’s metric? List and define the possible metrics to choose from? List and explain each routing protocol and the metric it uses. In the show ip route display where is the metric listed? What is the process used to forward packets when 2 or more paths have equal costs? Where can you look to determine if load balancing is RIP and IGRP EIGRP and OSPF a value used by routing protocols to assign costs to reach remote networks to determine which path is most preferable when there are multiple paths to the same remote network Hop count A combination of bandwidth and delay Bandwidth the number of routers a packet must cross to reach the destination network No they are not comparable Hop count - A simple metric that counts the number of routers a packet must traverse Bandwidth - Influences path selection by preferring the path with the highest bandwidth Load - Considers the traffic utilization of a certain link Delay - Considers the time a packet takes to traverse a path Reliability - Assesses the probability of a link failure, calculated from the interface error count or previous link failures Cost - A value determined either by the IOS or by the network administrator to indicate preference for a route. Cost can represent a metric, a combination of metrics or a policy. RIP: Hop count - Best path is chosen by the route with the lowest hop count. IGRP and EIGRP: Bandwidth, Delay, Reliability, and Load - Best path is chosen by the route with the smallest composite metric value calculated from these multiple parameters. By default, only bandwidth and delay are used. IS-IS and OSPF: Cost - Best path is chosen by the route with the lowest cost. . Cisco's implementation of OSPF uses bandwidth. The second value in the brackets. Load balancing The routing table and look for multiple paths to the same destination network being used? What are the possible values for Administrative Distance? What is the best value for administrative distance? What type of route has the lowest possible administrative distance? What does an administrative distance of 255 mean? Where can you find the administrative distance in the show ip route output? How does a router choose the best path if two routing protocols are being used? What are the two commands in which you can determine what the administrative distance is? What is the administrative distance for a static route? If you configure a route to a destination also learned by a dynamic routing protocol, what would you set the administrative distance to? What command can be issued to see the AD of a specific route? Can you change the AD of a directly connected route? What command can be issued to see the AD of a directly connected route? This is excellent practice for the exam. These are easy questions to right and if you practice they are easy to answer. 3.4.1 3.4.1.2 3.4.3 3.4.4 3.5.1 0 to 255 0 A directly connected network The router will not believe the route and will not install it in it’s routing table The first number in the brackets Administrative distance Show ip route Show ip protocols 1 Greater than that of the routing protocol Show ip route [route] no Show ip route [route] Administrative distance is an integer value that is used to indicate a router’s “trustworthiness” - In general, the smaller the AD, the trustworthy the routing protocol. Metrics are used by dynamic routing protocols to calculate the best path to a destination. - In general, the smaller the metric, the better the path. * Make sure you understand the principle of routing process. When a router received a packet and it sees there are multiple routes available in the routing table, it will decide how to route the packet based on 1) The longest bit that match between the packet and the entries in the routing table. If not then go to the next step. 2) Check for the lowest administrative distance. If there is a lower one, it will use it. If they are tie, then go to next step. 3) Check for the lowest metric. If there is a lower one, it will use it. If they are tie, then go to next step. 4) Now, you have equal-cost load balancing. The next thing you need to decide whether you have per destination or per packet load balancing. (Unequal cost load balancing is a difference process,) 5) EIGRP can be tweaked and run unequal cost load balancing, but by default they still using equal cost load balancing. * The following is the example of equal cost in RIP. What is the purpose of listing 2 entries under one network statement? * What is "routing protocol"? What is the purpose of "dynamic routing protocol"? * What is administrative distance? How does it get used to decide the route get used in the router? * What is metric? How does it get used to decide the route get used in the router? * Refer to the graphic below, when PC2 wants to access PC5, and you have multiple ways to get to it, but there exist only one prefer route and the other route will not get used? - Which route is the prefer route? Why? * You need to memorize the following properties: Static route: AD: ______ Metric:______ Connected route: AD: ______ Metric:______ RIP route: AD: ______ Metric:_____________ (name of the metric variable) OSPF route: AD: ______ Metric:___________ (name of the metric variable) EIGRP route: AD: ______ Metric:__________ (name of the metric variable) * You need to be able to dissect and understand the “show ip route” output: For example: - R 220.165.201.0/24 [120/3] via 192.168.25.2, 00:00:16, S0/0/0 - What is the significant of the information R? - What is the significant of the information 220.165.201.0? - What is the significant of the information /24? - What is the significant of the information 120? - What is the significant of the information 3? - What is the significant of the information 192.168.25.2? - What is the significant of the information S0/0/0? - O 10.10.1.0/27 [110/65] via 192.168.1.5, 00:00:05, Serial0/0/1 - What is the significant of the information O? - What is the significant of the information 10.10.1.0? - What is the significant of the information /27? - What is the significant of the information 110? - What is the significant of the information 65? - What is the significant of the information 192.168.1.5? - What is the significant of the information S0/0/1? * What types of routing protocols are proprietary routing protocols? * What types of routing protocols are none-proprietary routing protocols? What does proprietary means? * What is classful routing protocol? What is classless routing protocol? - What is the difference between classful and classless routing protocol? - Which type of routing protocols requires networks to have the same mask? - Which type of routing protocols allows networks to have the different mask? * What is load balancing? What command can you use to check whether your router has configured to use load balancing to distribute your packets? * What are the characteristics of "distance vector" routing protocol? * What are the characteristics of "link state" routing protocol? * What are the advantage and disadvantage of static routing? * What are the advantage and disadvantage of dynamic routing? * When consider to install a network routing protocol, under what circumstance would you choose to use "distance vector" routing protocol" over "link state" routing protocol? On the other hand, under what circumstance would you choose to use "link state" routing protocol" over "distance vector" routing protocol? Distance vector protocols work best in situations where: – The network is simple and flat and does not require a special hierarchical design. – The administrators do not have enough knowledge to configure and troubleshoot link-state protocols. – Specific types of networks, such as hub-and-spoke networks, are being implemented. – Worst-case convergence times in a network are not a concern. Link-state protocols work best in situations where: – The network design is hierarchical, usually occurring in large networks. – The administrators have a good knowledge of the implemented link-state routing protocol. – Fast convergence of the network is crucial. * What does it mean by networks in the router are converged? * Why is fast convergence a desirable characteristic of routing protocol? Can the router forward packet before networks get converged with other router? Why? Why not? Is there any downside of this action? * What commands do you need to create a "Connected" route in the routing table? Example: Router(config)# interface "type" Router(config-if)# ip address "x.x.x.x y.y.y.y" Router(config-if)# no shutdown * What commands do you need to create a "static" route in the routing table? Router(config)# ip route [Remote network + network mask] [exit interface (or) next hop IP] * You need to be able to count the metric in RIP. Why the metric in the following diagram is 2?