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Chapter 3 Routing Dynamically

Chapter 3 Routing Dynamically. CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College graziani@cabrillo.edu Version 6. Chapter 3. 3.1 Dynamic Routing Protocols 3.2 Distance Vector Dynamic Routing 3.3 RIP and RIPng Routing 3.4 Link-State Dynamic Routing

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Chapter 3 Routing Dynamically

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  1. Chapter 3Routing Dynamically CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College graziani@cabrillo.edu Version 6

  2. Chapter 3 • 3.1 Dynamic Routing Protocols • 3.2 Distance Vector Dynamic Routing • 3.3 RIP and RIPng Routing • 3.4 Link-State Dynamic Routing • 3.5 The Routing Table • 3.6 Summary

  3. Chapter 3: Objectives • Explain the basic operation of dynamic routing protocols. • Compare and contrast dynamic and static routing. • Determine which networks are available during an initial network discovery phase. • Define the different categories of routing protocols. • Describe the process by which distance vector routing protocols learn about other networks. • Identify the types of distance-vector routing protocols. • Configure the RIP routing protocol. • Configure the RIPng routing protocol. • Explain the process by which link-state routing protocols learn about other networks.

  4. Dynamic Routing Protocols

  5. Types of Routing Protocols Exterior Gateway Protocols Interior Gateway Protocols Distance Vector Link State Path Vector IPv4 IPv6 * OSPFv3 supports routing both IPv4 and IPv6.

  6. Distance Vector Routing Protocol Operation • What does a street sign like this tell you? • How far (distance) • Which way (direction) • Distance vector • Routes are advertised as vectors of distance and direction. • Distance is defined in terms of a metric • Such as hop count • Direction is simply the: • Nexthop router or • Exit interface • Typically use the Bellman-Ford algorithm for the best-path (shortest) route determination

  7. Distance Vector Routing Protocol Operation • Routing protocol • Does not know the topology of an internetwork. • Only knows the routing information received from its neighbors. • Does not know if another path would actually be faster. I don’t have a map of the network. Would another path that is longer actually be faster? (speed limit) All I know is how far and which direction (to next hop router) Distance Vector routing protocols are like signposts along the path to the final destination.

  8. Distance Vector Concepts

  9. Distance Vector Routing Protocols • Routing Information Protocol (RIP) • Thee versions: IPv4 RIPv1 and RIPv2. RIPng for IPv6. • Uses hop counts as its metric. • Still around but don't use. • Interior Gateway Routing Protocol (IGRP) • Legacy Cisco Proprietary protocol. • Uses bandwidth and delay as its metric. • Enhanced IGRP (EIGRP) • Cisco Proprietary protocol. • Uses bandwidth and delay as its metric.

  10. Link-State Protocol Operation OR • Link-state routing protocol can create a “complete view,” or topology, of the network. • Link-state protocols are associated with Shortest Path First (SPF) calculations. • A link-state router uses the link-state information to: • Create a topology map • Select the best path to all destination networks in the topology. • Each router makes the decision! Link State routing protocols is like having a complete map of the network topology

  11. Link-State Protocol Operation • 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.

  12. Link-State Routing Protocols • Open Shortest Path First (OSPF) • Popular standards based routing protocol • Intermediate System-to-Intermediate System (IS-IS) • Popular in provider networks

  13. Link-State Concepts

  14. Evolution of Dynamic Routing Protocols Classful Routing Protocols Classless Routing Protocols BGP-MP & OSPFv3 OSPFv2 RIPng RIPv2 EGP IS-ISv6 RIPv1 BGP IGRP IS-IS EIGRP

  15. Purpose of Dynamic Routing Protocols Dynamic Routing Protocol Add dynamic routing protocol… • The purpose of dynamic routing protocols includes: • 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 No changes!

  16. Main Components of Routing Protocols Data Structures • Neighbor table • Topology table • Neighbortable • Topology table EIGRP Hello EIGRP Update Routing Protocol Messages Algorithm I will use the EIGRP DUAL algorithm to identify what the best routes are. I will use the EIGRP DUAL algorithm to identify what the best routes are.

  17. Dynamic Routing Protocol Operation Update Update Update Update Update Update • In general, the operations of a dynamic routing protocol can be described as follows: • 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 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.

  18. Dynamic versus Static Routing

  19. Using Static Routing R2(config)# ip route 172.16.3.0 255.255.255.0 172.16.2.2 • Static routing has several primary uses: • Best for smaller networks that are not expected to grow significantly. • Routing to and from a stub network. • A default route. • Networks typically use a combination of both static and dynamic routing. R1(config)# ip route 0.0.0.0 0.0.0.0 172.16.2.1

  20. Dynamic Routing Scenario • Dynamic routing is the best choice for large networks • Dynamic routing protocols help the network administrator manage the network: • Providing redundant paths • Automatically implementing the alternate path when a link goes down. Networks often use both static and dynamic routing.

  21. Reaching Remote Networks Dynamically • Hey I’m R1 and I’m using EIGRP to let my neighbors know that I’m directly connected to networks: • 192.168.10.0/24 • 192.168.11.0/24 • 209.165.200.224/30 Internet • Hey I’m R2 and I’m using EIGRP to let my neighbors know that I’m the gateway to the Internet (I have a default route to the Internet) and that I’m directly connected to: • 10.1.1.0/24 • 10.1.2.0/24 • 209.165.200.224/30

  22. Routing Information Protocol (RIP)

  23. Why RIP? • RIP is rarely used in modern networks! • However, it’s useful as a foundation for understanding basic network routing. • This section provides a brief overview of how to configure basic RIP settings and to verify RIPv2.

  24. RIP Cheat Sheet

  25. RIP Reference Topology 192.168.3.0/24 192.168.5.0/24 192.168.1.0/24 .1 G0/0 DCE DCE .1 .1 S0/0/1 S0/0/0 S0/0/0 S0/0/1 R2 R3 G0/0 R1 G0/0 .1 .2 .2 .1 192.168.2.0/30 192.168.4.0/30 G0/0 G0/0 G0/0

  26. Dynamic versus Static RoutingRouter RIP Configuration Mode • Use the router rip command to enable RIP v1 • Use the no router rip command to disable RIP

  27. Configuring the RIP ProtocolAdvertise Networks • The network network-address router configuration mode command: • Enables RIP on all interfaces that belong to a specific network • Advertises the network in RIP routing updates sent to other routers every 30 seconds. Note: RIPv1 is a classful routing protocol for IPv4.

  28. Configuring the RIP ProtocolVerify RIP Routing show ip route – displays RIP routes installed in the routing table. show ip protocols – displays IPv4 routing protocols configured on the router.

  29. Configuring the RIP ProtocolEnable and Verify RIPv2 • Use the version 2 router configuration mode command to enable RIPv2 • Use the show ip protocols command to verify that RIPv2 is configured. • Use the show ip route command to verify the RIPv2 routes in the routing table.

  30. Configuring the RIP ProtocolDisable Auto Summarization • RIPv2 automatically summarizes networks at major network boundaries. • Use the no auto-summary router configuration mode command to disable auto summarization. • Use the show ip protocols command to verify that auto summarization is off.

  31. Configuring the RIP ProtocolConfigure Passive Interfaces • RIP updates: • Are forwarded out all RIP-enabled interfaces by default. • Only need to be sent out interfaces that are connected to other RIP-enabled routers. • Sending RIP updates to LANs wastes bandwidth, wastes resources, and is a security risk. • Use the passive-interface router configuration command to stop routing updates out the interface. Still allows that network to be advertised to other routers.

  32. Configuring the RIP ProtocolPropagate a Default Route • In the diagram a default static route to the Internet is configured on R1. • The default-information originate router configuration command instructs R1 to send the default static route information in the RIP updates.

  33. RIP Passive Interfaces 192.168.3.0/24 192.168.5.0/24 192.168.1.0/24 .1 G0/0 DCE DCE .1 .1 S0/0/1 S0/0/0 S0/0/0 S0/0/1 R2 R3 G0/0 R1 G0/0 .1 .2 .2 .1 192.168.2.0/30 192.168.4.0/30 • Sending out unneeded updates on a LAN: • Wastes Bandwidth  • Wastes Resources • Security Risk  • The passive-interface • Stops routing updates out the specified interface. • The network that the specified interface belongs to is still advertised in routing updates that are sent out other interfaces. • Should be configured on interfaces which do not connect to other RIP routers.

  34. IPv4 Routing Table

  35. Understanding the IPv4 Routing Table • For more details: Cisco IP Routing, by Alex Zinin (ISBN 0-201-60473-6)

  36. It is all because of classful IPv4 addressing

  37. Back in the day…. When you got classful address, you got the whole thing Class A 10.0.0.0/8 Class B 172.16.0.0/16 Class C 192.168.1.0/24 Class B 172.17.0.0/16 Class C 192.168.2.0/24 Class A 11.0.0.0/8 Class A 12.0.0.0/8 Class B 172.18.0.0/16 Class C 192.168.3.0/24

  38. R1#show ip route S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# • So, the IPv4 routing table is organized by classful addresses

  39. Level 1 route • A level 1 route is a route with a subnet mask equal to or less than the classful mask of the network address.

  40. R1#show ip route S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# • Level 1 Ultimate route: a route with a subnet mask equal to or less than the classful mask of the network address.

  41. R1#show ip route S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# • Level 1 Parent route: A parent route is a heading: • Indicates the presence oflevel 2 routes, also known as child routes. • Level 1 parent route is automatically created any time a subnet is added to the routing table. • A parent route is created whenever a route with a mask greater than the classful mask is entered into the routing table.

  42. If Classful Parent matches, check Children for more specific match. If no Children match look for a lesser match. RTC# show ip route Gateway of last resort is 192.168.1.1 to network 0.0.0.0 R 192.168.10.0/24 [120/1] via 192.168.1.1, 00:00:02, Serial1 C 192.168.1.0/24 is directly connected, Serial1 C 192.168.2.0/24 is directly connected, Ethernet0 172.30.0.0/24 is subnetted, 3 subnets C 172.30.2.0 is directly connected, Loopback2 C 172.30.3.0 is directly connected, Loopback3 C 172.30.1.0 is directly connected, Loopback1 S* 0.0.0.0/0 [1/0] via 192.168.1.1 RTC# ping 172.30.4.1 Sending 5, 100-byte ICMP Echoes to 172.30.4.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5),round-trip min/avg/max=56/57/60 ms Packet’s Destination IP Address: 172.30.4.1

  43. Routing Table Lookup Process IP Packet Routing Table • /prefix-length in the route indicates the number of bits that must match the destination IPv4 address for this route to be a match Find “best match”

  44. A packet is destined for 172.16.0.10 • The router has three possible routes that match this packet: • 172.16.0.0/12 • 172.16.0.0/18 • 172.16.0.0/26 • Of the three routes, 172.16.0.0/26 has the longest match and is therefore chosen to forward the packet.

  45. R1#show ip route | begin Gateway Gateway of last resort is 209.165.200.234 to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 192.168.1.100 • Packet with Destination IPv4 address 192.168.1.100 • One Level 1 Ultimate Routes to choose from. • 192.168.0.0/16 is the best (only) match, the longest match (coming). • Longest match: Most left-most bits that match between destination IP address and route in routing table • At a minimum it must match the number of bits in the route as indicated by the subnet mask.

  46. R1#show ip route | begin Gateway Gateway of last resort is 209.165.200.234 to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 172.16.3.10 • Packet with Destination IPv4 address 172.16.3.10 • No Level 1 Ultimate Routes match • Matches Level 1 Parent Route (minimum match is classful mask). • Look for matching Child route • At a minimum it must match the number of bits in the route as indicated by the subnet mask. • If more than one child route matches choose routes with longest match.

  47. R1#show ip route | begin Gateway Gateway of last resort is 209.165.200.234 to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 172.16.5.10 • Packet with Destination IPv4 address 172.16.5.10

  48. R1#show ip route | begin Gateway Gateway of last resort is 209.165.200.234 to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 209.165.200.234, Serial0/0/1 is directly connected, Serial0/0/1 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 10.1.2.3 • Packet with Destination IPv4 address 10.1.2.3 • No Level 1 Ultimate Routes to choose match • No Level 1 Parent Routes match • Look for Level 1 supernet route (mask less than classful mask), including default • Choose longest match. • Default route always matches because 0 bits have to match. • 0 matching bits makes it the “gateway of last resort”

  49. R1#show ip route | begin Gateway 172.16.0.0/16 is variably subnetted, 5 subnets, 3 masks C 172.16.1.0/24 is directly connected, GigabitEthernet0/0 L 172.16.1.1/32 is directly connected, GigabitEthernet0/0 R 172.16.2.0/24 [120/1] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.3.0/24 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 172.16.4.0/28 [120/2] via 209.165.200.226, 00:00:12,Serial0/0/0 R 192.168.0.0/16 [120/2] via 209.165.200.226, 00:00:03, Serial0/0/0 209.165.200.0/24 is variably subnetted, 5 subnets, 2 masks C 209.165.200.224/30 is directly connected, Serial0/0/0 L 209.165.200.225/32 is directly connected, Serial0/0/0 R 209.165.200.228/30 [120/1]via209.165.200.226,0:0:12,Serial0/0/0 C 209.165.200.232/30 is directly connected, Serial0/0/1 L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 10.1.2.3 • Packet with Destination IPv4 address 10.1.2.3 • No default route • No Level 1 Ultimate Routes to choose match • No Level 1 Parent Routes match • No supernet routes match • Drop packet

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