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CCNA2-1 Chapter 3 Introduction to Dynamic Routing Protocols.

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Presentation on theme: "CCNA2-1 Chapter 3 Introduction to Dynamic Routing Protocols."— Presentation transcript:

1 CCNA2-1 Chapter 3 Introduction to Dynamic Routing Protocols

2 CCNA2-2 Chapter 3 Note for Instructors These presentations are the result of a collaboration among the instructors at St. Clair College in Windsor, Ontario. These presentations are the result of a collaboration among the instructors at St. Clair College in Windsor, Ontario. Thanks must go out to Rick Graziani of Cabrillo College. His material and additional information was used as a reference in their creation. Thanks must go out to Rick Graziani of Cabrillo College. His material and additional information was used as a reference in their creation. If anyone finds any errors or omissions, please let me know at: If anyone finds any errors or omissions, please let me know at:

3 CCNA2-3 Chapter 3 Introduction to Dynamic Routing Protocols

4 CCNA2-4 Chapter 3 Perspective and Background Dynamic routing protocols have evolved over several years. Dynamic routing protocols have evolved over several years. As networks have evolved and become more complex, new routing protocols have emerged. As networks have evolved and become more complex, new routing protocols have emerged. The first version of RIP was released in 1982, but some of the basic algorithms within the protocol were used on the ARPANET as early as The first version of RIP was released in 1982, but some of the basic algorithms within the protocol were used on the ARPANET as early as 1969.

5 CCNA2-5 Chapter 3 Role of Dynamic Routing Protocol Exchange of routing information between routers. Exchange of routing information between routers. Dynamically learn information about remote networks and add routes to routing tables.Dynamically learn information about remote networks and add routes to routing tables. Determines the best path to each network.Determines the best path to each network. Automatically finds alternate paths if needed.Automatically finds alternate paths if needed.

6 CCNA2-6 Chapter 3 Role of Dynamic Routing Protocol Advantages over Static Routes: Advantages over Static Routes: Less administrative overhead.Less administrative overhead. Scales better.Scales better. Less prone to configuration errors.Less prone to configuration errors.

7 CCNA2-7 Chapter 3 Network Discovery and Routing Table Components of Dynamic Routing Protocols: Components of Dynamic Routing Protocols: Data Structures:Data Structures: Tables or databases for their operations, kept in RAM.Tables or databases for their operations, kept in RAM. Algorithm:Algorithm: An algorithm is a finite list of steps used in accomplishing a task.An algorithm is a finite list of steps used in accomplishing a task. Used for processing routing information and for best- path determination.Used for processing routing information and for best- path determination. Routing Protocol Messages:Routing Protocol Messages: Discover neighboring routers.Discover neighboring routers. Exchange, learn and maintain accurate network routing information.Exchange, learn and maintain accurate network routing information.

8 CCNA2-8 Chapter 3 Dynamic Routing vs Static Routing

9 CCNA2-9 Chapter 3 Introduction to Dynamic Routing Protocols Classifying Dynamic Routing Protocols

10 CCNA2-10 Chapter 3 Classifying Dynamic Routing Protocols Interior Gateway Exterior Gateway Distance Vector Link State Path Vector ClassfulRIPIGRPEGP ClasslessRIPv2EIGRPOSPFv2IS-ISBGPv4 IPv6RIPng EIGRP for IPv6 OSPFv3 IS-IS for IPv6 BGPv4 for IPv6

11 CCNA2-11 Chapter 3 Classifying Dynamic Routing Protocols Concept of Autonomous Systems (AS): Concept of Autonomous Systems (AS): A network or group of networks identified and administered as a single entity.

12 CCNA2-12 Chapter 3 Classifying Dynamic Routing Protocols IGP vs. EGP Routing Protocols: IGP vs. EGP Routing Protocols: Allow one AS to exchange routing information with another AS. Allow routers within an AS to exchange information.

13 CCNA2-13 Chapter 3 Interior Gateway Exterior Gateway Distance Vector Link State Path Vector ClassfulRIPIGRPEGP ClasslessRIPv2EIGRPOSPFv2IS-ISBGPv4 IPv6RIPng EIGRP for IPv6 OSPFv3 IS-IS for IPv6 BGPv4 for IPv6 Interior Gateway Exterior Gateway Distance Vector Link State Path Vector ClassfulRIPIGRPEGP ClasslessRIPv2EIGRPOSPFv2IS-ISBGPv4 IPv6RIPng EIGRP for IPv6 OSPFv3 IS-IS for IPv6 BGPv4 for IPv6 Classifying Dynamic Routing Protocols

14 CCNA2-14 Chapter 3 Distance Vector and Link State Distance Vector: Distance Vector: Routes are advertised as vectors of distance and direction.Routes are advertised as vectors of distance and direction. Distance:Distance: Is defined in terms of a metric.Is defined in terms of a metric. Hop Count: The number of routers between the source and destination networks.Hop Count: The number of routers between the source and destination networks. Direction:Direction: Is simply the next-hop router or exit interface.Is simply the next-hop router or exit interface. Routing updates usually consist of periodic updates of the entire routing table. (e.g.. Routing Information Protocol - RIP – every 30 seconds)Routing updates usually consist of periodic updates of the entire routing table. (e.g.. Routing Information Protocol - RIP – every 30 seconds)

15 CCNA2-15 Chapter 3 Distance Vector and Link State Distance Vector: Distance Vector: or update timer expires

16 CCNA2-16 Chapter 3 Distance Vector and Link State Distance Vector: Distance Vector: The network is simple and flat and does not require a hierarchical design.The network is simple and flat and does not require a hierarchical design. The administrators do not have enough knowledge to configure and troubleshoot link-state protocols.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.Specific types of networks, such as hub-and-spoke networks, are being implemented. Worst-case convergence times in a network are not a concern.Worst-case convergence times in a network are not a concern.

17 CCNA2-17 Chapter 3 Distance Vector and Link State Link State: Link State: A Link State routing protocol can create a complete map of the network topology.A Link State routing protocol can create a complete map of the network topology. A link-state router:A link-state router: Receives an update.Receives an update. Builds a topology database.Builds a topology database. Uses a Shortest Path First (SPF) algorithm to create its view of the network.Uses a Shortest Path First (SPF) algorithm to create its view of the network. Builds the routing table.Builds the routing table. Routing updates (not the entire table) are only sent to neighbouring routers when the topology changes. (e.g.. Open Shortest Path First - OSPF)Routing updates (not the entire table) are only sent to neighbouring routers when the topology changes. (e.g.. Open Shortest Path First - OSPF)

18 CCNA2-18 Chapter 3 Distance Vector and Link State Link State: Link State:

19 CCNA2-19 Chapter 3 Distance Vector and Link State Link State: Link State: The network design is hierarchical, usually occurring in large networks.The network design is hierarchical, usually occurring in large networks. The administrators have a good knowledge of the implemented link-state routing protocol.The administrators have a good knowledge of the implemented link-state routing protocol. Fast convergence of the network is crucial.Fast convergence of the network is crucial.

20 CCNA2-20 Chapter 3 Interior Gateway Exterior Gateway Distance Vector Link State Path Vector ClassfulRIPIGRPEGP ClasslessRIPv2EIGRPOSPFv2IS-ISBGPv4 IPv6RIPng EIGRP for IPv6 OSPFv3 IS-IS for IPv6 BGPv4 for IPv6 Classifying Dynamic Routing Protocols

21 CCNA2-21 Chapter 3 Classful and Classless Classful Protocols: Classful Protocols: Do not send subnet mask information in routing updates.Do not send subnet mask information in routing updates. The subnet mask must be the same throughout the entire topology.The subnet mask must be the same throughout the entire topology. IP Addresses were first allocated based on classes (A, B or C).IP Addresses were first allocated based on classes (A, B or C). The first routing protocols (RIP) did not need to transmit the subnet mask because of the address class distinction.The first routing protocols (RIP) did not need to transmit the subnet mask because of the address class distinction. Network mask could be determined based on value of first octet of the network address.Network mask could be determined based on value of first octet of the network address. VLSM and CIDR are not possible.VLSM and CIDR are not possible.

22 CCNA2-22 Chapter 3 Classful and Classless Classless Protocols: Classless Protocols: Include subnet mask information in routing updates.Include subnet mask information in routing updates. The subnet mask does not have to be the same throughout the entire topology.The subnet mask does not have to be the same throughout the entire topology. Today’s networks are no longer allocated based on the address class.Today’s networks are no longer allocated based on the address class. The subnet mask can no longer be determined by the first octet of the IP Address.The subnet mask can no longer be determined by the first octet of the IP Address. VLSM and CIDR are possible.VLSM and CIDR are possible.

23 CCNA2-23 Chapter 3 Interior Gateway Exterior Gateway Distance Vector Link State Path Vector ClassfulRIPIGRPEGP ClasslessRIPv2EIGRPOSPFv2IS-ISBGPv4 IPv6RIPng EIGRP for IPv6 OSPFv3 IS-IS for IPv6 BGPv4 for IPv6 Classifying Dynamic Routing Protocols

24 CCNA2-24 Chapter 3 Dynamic Routing Protocols and Convergence Convergence: Convergence: The network has converged when all routers have complete and accurate information about the network.The network has converged when all routers have complete and accurate information about the network. The speed of convergence is an important characteristic of a network.The speed of convergence is an important characteristic of a network.

25 CCNA2-25 Chapter 3 Dynamic Routing Protocols and Convergence Convergence: Convergence: The routers must:The routers must: Share routing information.Share routing information. Calculate the best path to a destination.Calculate the best path to a destination. Update their routing tables.Update their routing tables.

26 CCNA2-26 Chapter 3 Dynamic Routing Protocols and Convergence Convergence: Convergence: Generally:Generally: Slower Convergence: RIPSlower Convergence: RIP Faster Convergence: EIGRP and OSPFFaster Convergence: EIGRP and OSPF

27 CCNA2-27 Chapter 3 Introduction to Dynamic Routing Protocols Metrics ? ? ?

28 CCNA2-28 Chapter 3 Purpose of a Metric There are times when a router will have multiple paths to the same destination. There are times when a router will have multiple paths to the same destination. Metrics are a way to measure and/or compare routes to determine which route is the best path. Metrics are a way to measure and/or compare routes to determine which route is the best path. ? To route to..

29 CCNA2-29 Chapter 3 Purpose of a Metric The route chosen will depend on two things: The route chosen will depend on two things: The routing protocol in use.The routing protocol in use. The metric used by the routing protocol.The metric used by the routing protocol. ? To route to..

30 CCNA2-30 Chapter 3 Metrics and Routing Protocols Routing Information Protocol (RIP): Routing Information Protocol (RIP): Uses hop count as its metric. Lower is better.Uses hop count as its metric. Lower is better /24 Network is: 1 hop via R2 1 hop via R2 2 hops via R3 2 hops via R3 This is the route I will use.

31 CCNA2-31 Chapter 3 Metrics and Routing Protocols Open Shortest Path First (OSPF): Open Shortest Path First (OSPF): Uses bandwidth as its metric. Faster is better.Uses bandwidth as its metric. Faster is better /24 The route to network /24 is: 56 Kbps through R2 56 Kbps through R Kbps through R Kbps through R3 This is the route I will use.

32 CCNA2-32 Chapter 3 Metric Filed in the Routing Table The routing table displays the metric for each dynamic and static route. The routing table displays the metric for each dynamic and static route. Dynamic routes with the lowest metric are installed by routing protocols.Dynamic routes with the lowest metric are installed by routing protocols. Static routes always have a metric of 0.Static routes always have a metric of 0.

33 CCNA2-33 Chapter 3 Metric Field in the Routing Table All routers are running RIP. All routers are running RIP. R2 has a route to and is 2 hops away. R2 has a route to and is 2 hops away.

34 CCNA2-34 Chapter 3 Load Balancing What happens when two or more routes to the same destination have identical metric values? What happens when two or more routes to the same destination have identical metric values? The router load balances among all equal-cost paths. The router load balances among all equal-cost paths.

35 CCNA2-35 Chapter 3 Introduction to Dynamic Routing Protocols Administrative Distance

36 CCNA2-36 Chapter 3 Purpose of Administrative Distance (AD) Routers learn about adjacent networks that are directly connected and about remote networks by using static routes and dynamic routing protocols. Routers learn about adjacent networks that are directly connected and about remote networks by using static routes and dynamic routing protocols. A router might learn of a route to the same network from more than one source. A router might learn of a route to the same network from more than one source.

37 CCNA2-37 Chapter 3 Purpose of Administrative Distance (AD) Routers learn about adjacent networks that are directly connected and about remote networks by using static routes and dynamic routing protocols. Routers learn about adjacent networks that are directly connected and about remote networks by using static routes and dynamic routing protocols. A router might learn of a route to the same network from more than one source. A router might learn of a route to the same network from more than one source. Three types of Routing Sources. Three types of Routing Sources. Direct ConnectDirect Connect StaticStatic Dynamic Routing ProtocolDynamic Routing Protocol Route SourceAD Direct Connect0 Static1 EIGRP Summary5 External BGP20 Internal EIGRP90 OSPF110 IS-IS115 RIP120 External EIGRP170 Internal BGP200

38 CCNA2-38 Chapter 3 Purpose of Administrative Distance (AD) Administrative Distance is used to determine which route is to be installed in the routing table. Administrative Distance is used to determine which route is to be installed in the routing table. The route that has the lower AD will be preferred over the route with the higher AD and will be added to the routing table. The route that has the lower AD will be preferred over the route with the higher AD and will be added to the routing table. The term trustworthy is commonly used when defining administrative distance. The term trustworthy is commonly used when defining administrative distance. The lower the administrative distance value, the more “trustworthy” the route.The lower the administrative distance value, the more “trustworthy” the route. Route SourceAD Direct Connect0 Static1 EIGRP Summary5 External BGP20 Internal EIGRP90 OSPF110 IS-IS115 RIP120 External EIGRP170 Internal BGP200

39 CCNA2-39 Chapter 3 Multiple Routing Sources For Example: For Example: A route to a network is learned by the configuration of a static route.A route to a network is learned by the configuration of a static route. Another route (or the same route) to the same network is learned when OSPF is enabled on the router.Another route (or the same route) to the same network is learned when OSPF is enabled on the router. Static Route AD = 1Static Route AD = 1 OSPF AD = 110OSPF AD = 110 The static route will be added to the routing table and the route learned from OSPF will be ignored.The static route will be added to the routing table and the route learned from OSPF will be ignored. Route SourceAD Direct Connect0 Static1 EIGRP Summary5 External BGP20 Internal EIGRP90 OSPF110 IS-IS115 RIP120 External EIGRP170 Internal BGP200

40 CCNA2-40 Chapter 3 Multiple Routing Sources While not as common, R2 above has learned routes to network /24 from EIGRP (AD 90) and from RIP (AD 120). While not as common, R2 above has learned routes to network /24 from EIGRP (AD 90) and from RIP (AD 120). The route learned from EIGRP will be installed in the routing table. The route learned from EIGRP will be installed in the routing table.

41 CCNA2-41 Chapter 3 Verifying Administrative Distance (AD) show ip route show ip route AD = 0

42 CCNA2-42 Chapter 3 Verifying Administrative Distance (AD) show ip protocols show ip protocols

43 CCNA2-43 Chapter 3 Static Routes and Administrative Distance Static Route AD = 1 Static Route AD = 1 After directly connected networks (AD = 0), static routes are the most preferred route source.After directly connected networks (AD = 0), static routes are the most preferred route source.

44 CCNA2-44 Chapter 3 Static Routes and Administrative Distance Routing table display depends on how you issued the command. The AD for both of these is 1! Routing table display depends on how you issued the command. The AD for both of these is 1! Exit Interface: ip route serial 0/0/0 Next-hop Address: ip route

45 CCNA2-45 Chapter 3 Directly Connected and Administrative Distance Appear in the routing table as soon as the interface is active with an IP address and subnet mask (“up” and “up”). Appear in the routing table as soon as the interface is active with an IP address and subnet mask (“up” and “up”). AD = 0 is the most preferred route.AD = 0 is the most preferred route. Cannot be changedCannot be changed No other type of route can have AD = 0.No other type of route can have AD = 0. There is no better route for a router than having one of its interfaces directly connected to that network. There is no better route for a router than having one of its interfaces directly connected to that network.

46 CCNA2-46 Chapter 3 Directly Connected and Administrative Distance To see the AD value of any network, use the command show ip route [route] option. To see the AD value of any network, use the command show ip route [route] option. Directly ConnectedDirectly Connected StaticStatic Dynamic Routing ProtocolDynamic Routing Protocol


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