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Chapter 5 RIP version 1 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College Last Updated: 3/10/2009.

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Presentation on theme: "Chapter 5 RIP version 1 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College Last Updated: 3/10/2009."— Presentation transcript:

1 Chapter 5 RIP version 1 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College Last Updated: 3/10/2009

2 2 Note This presentation will be updated prior to March. 25, 2008 The audio of the lecture for this presentation will be available on my web site after March. 25, 2008 My web site is For access to these PowerPoint presentations and other materials, please me at

3 3 For further information This presentation is an overview of what is covered in the curriculum/book. For further explanation and details, please read the chapter/curriculum. Book:  Routing Protocols and Concepts  By Rick Graziani and Allan Johnson  ISBN:  ISBN-13:

4 4 Topics RIPv1: Distance Vector, Classful Routing Protocol  Background and Perspective  RIPv1 Characteristics and Message Format  RIP Operation Basic RIPv1 Configuration  RIPv1 Scenario A  Enable RIP: router rip Command  Specifying Networks Verification and Troubleshooting  Verifying RIP: show ip route  Verifying RIP: show ip protocols  Verifying RIP: debu ip rip  Passive Interfaces Automatic Summarization  Modified Topology B  Boundary Routers and Automatic Summarization  Processing RIP Updates  Sending RIP Updates  Advantages and Disadvantages of Automatic Summarization Default Route and RIPv1  Modified Topology C  Propagating the Default Route in RIPv1

5 5 RIPv1 Download Packet Tracer Topology: cis82-RIPv1-A-student.pkt

6 RIPv1: A Distance Vector, Classful Routing Protocol Background and Perspective RIPv1 Characteristics and Message Format RIP Operation

7 7 RIPv1: Distance Vector, Classful Routing Protocol Why learn RIP?  Still in use today.  Help understand fundamental concepts and comparisons of protocols  Classful (RIPv1) vs classless (RIPv2)

8 8 Background and Perspective RIP is not a protocol “on the way out.” In fact, an IPv6 form of RIP called RIPng (next generation) is now available..

9 9 Background and Perspective Charles Hedrick wrote RFC 1058 in 1988, in which he documented the existing protocol and specified some improvements. RFC 1058 can be found at

10 10 RIPv1 Characteristics and Message Format RIP characteristics:  Distance Vector or Link State?  Distance vector routing protocol.  Metric?  Hop count  Maximum Hop count?  Greater than 15 are considered unreachable.  Routing table updates are broadcasted every…?  30 seconds. (RIPv2 uses multicasts)

11 11 RIPv1 Characteristics and Message Format

12 12 RIPv1 Characteristics and Message Format

13 13 IP Address Classes and Classful Routing RIPv1:  Classful routing protocol.  Does not send subnet mask in update. No subnet mask

14 14 IP Address Classes and Classful Routing R2 receives an RIP update with a network address. R2 adds the network address and mask to the routing table. A router either uses the subnet mask: (discussed later)  Local interface or  Default classful subnet mask Because of this limitation, RIPv1 networks cannot be discontiguous, nor can they implement VLSM. RIP Update network-add Routing Table Network-add/mask /16 ?

15 Basic RIPv1 Configuration RIPv1 Scenario A Enable RIP: router rip Command Specifying Networks

16 16 RIPv1 is a classful or classless routing protocol?  Classful How many classful networks are there and of what class?  5 Class C network addresses. We will see that the class of the network is used by RIPv1 to determine the subnet mask. RIPv1 Scenario A

17 17 Enabling RIP: router rip Command What routing protocols does this router support? (PT is limited) Configure RIP… R1# conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)# router ? bgp Border Gateway Protocol (BGP) egp Exterior Gateway Protocol (EGP) eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) igrp Interior Gateway Routing Protocol (IGRP) isis ISO IS-IS iso-igrp IGRP for OSI networks mobile Mobile routes odr On Demand stub Routes ospf Open Shortest Path First (OSPF) rip Routing Information Protocol (RIP) R1(config)# router rip R1(config-router)#

18 18 Enabling RIP: router rip Command no router rip  To remove the RIP routing process from a device  Stops the RIP process  Erases all existing RIP configuration commands. R1# conf t R1(config)# router rip R1(config-router)# network R1(config-router)# network R1(config-router)# exit R1(config)# no router rip

19 19 To enable RIP routing for a network, use the network command in router configuration mode Enter the classful network address for each directly connected network. Router(config-router)# network directly-connected-classful- network-address Specifying Networks

20 20 The network command performs the following functions:  Enables RIP on all interfaces that belong to a specific network.  Associated interfaces will now both send and receive RIP updates.  Advertises the specified network in RIP routing updates sent to other routers every 30 seconds (no mask). R1(config)# router rip R1(config-router)# network R1(config-router)# network Specifying Networks RIP Update

21 21 Specifying Networks Configure RIP for all three routers What happens if you enter a subnet or host IP address? (Try it)  IOS automatically converts it to a classful network address.  For example, if you enter the command network , the router will convert it to network R1(config)# router rip R1(config-router)# network R1(config-router)# network R2(config)# router rip R2(config-router)# network R2(config-router)# network R2(config-router)# network R3(config)# router rip R3(config-router)# network R3(config-router)# network Only directly connected classful network addresses!

22 22 Only directly connected classful network addresses!

23 23 Administrative Distance What is the administrative distance of a network route learned via RIP?  120 R3# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R /24 [120/2] via , 00:00:13, Serial0/0/1 R /24 [120/1] via , 00:00:25, Serial0/0/1 R /24 [120/1] via , 00:00:25, Serial0/0/1 C /24 is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0 R3# R = RIP

24 24 Administrative Distance Where is the administrative distance displayed using this command? R3# show ip protocols Routing Protocol is “rip” Routing Information Sources: Gateway Distance Last Update :00:10 Distance: (default is 120)

25 Verification and Troubleshooting Verifying RIP: show ip route Verifying RIP: show ip protocols Verifying RIP: debu ip rip Passive Interfaces

26 26 Verifying RIP: show ip route on all three routers… R1# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, Gateway of last resort is not set R /24 [120/1] via , 00:00:02, Serial0/0/0 R /24 [120/2] via , 00:00:02, Serial0/0/0 C /24 is directly connected, FastEthernet0/0 C /24 is directly connected, Serial0/0/0 R /24 [120/1] via , 00:00:02, Serial0/0/0 The routing table, includes what kind of routes?  Directly connected networks  Static routes  Dynamic routes Why might a RIP route not be immediately displayed in the routing table?  Networks will take some time to converge.

27 27 Verifying RIP: show ip route Command R2# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, Gateway of last resort is not set C /24 is directly connected, Serial0/0/1 R /24 [120/1] via , 00:00:12, Serial0/0/1 R /24 [120/1] via , 00:00:24, Serial0/0/0 C /24 is directly connected, Serial0/0/0 C /24 is directly connected, FastEthernet0/0 Using R2, which routes do you expect to see in our scenario?  Directly connected networks of R2  RIP routes for remote networks What routes do you expect not to see?  Networks not in our scenario – not configured with network statements on the routers.  Static default route

28 28 Verifying RIP: show ip route Command R3# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, Gateway of last resort is not set C /24 is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0 R /24 [120/2] via , 00:00:08, Serial0/0/1 R /24 [120/1] via , 00:00:08, Serial0/0/1 R /24 [120/1] via , 00:00:08, Serial0/0/1

29 29 Verifying RIP: show ip route Command R1# show ip route R /24 [120/2] via , 00:00:23, Serial0/0/0

30 30 Examine and discuss the show ip protocols Command

31 31 Verifying RIP: show ip protocols Command Verifies that RIP routing is configured and running on Router R2 At least one active interface with an associated network command is needed before RIP routing will start.

32 32 Verifying RIP: show ip protocols Command These are the timers that show when the next round of updates will be sent out from this router—23 seconds from now, in the example.

33 33 Verifying RIP: show ip protocols Command This information relates to filtering updates and redistributing routes, if configured on this router. Filtering and redistribution are both CCNP-level topics.

34 34 Verifying RIP: show ip protocols Command Information about which RIP version is currently configured and which interfaces are participating in RIP updates.

35 35 Verifying RIP: show ip protocols Command Router R2 is currently summarizing at the classful network boundary By default, will use up to four equal-cost routes to load- balance. Automatic summarization is discussed later in this chapter.

36 36 Verifying RIP: show ip protocols Command Classful networks configured with the network command are listed next. These are the networks that R2 will include in its RIP updates. (with other learned routes)

37 37 Verifying RIP: show ip protocols Command RIP neighbors Gateway: Next-hop IP address of the neighbor that is sending R2 updates. Distance is the AD that R2 uses for updates sent by this neighbor. Last Update is the seconds since the last update was received from this neighbor.

38 38 Use debug ip rip to view RIP updates that are sent and received… The debug command is a useful tool to help diagnose and resolve networking problems, providing real-time, continuous information.

39 39 Assuming all routers have converged, why were no other routes from R1’s routing table sent to R2? Split horizon rule.  R1 is will not advertise networks back to R2 that were learned from R2. RIP: received v1 update from on Serial0/0/ in 1 hops

40 40 RIP: received v1 update from on Serial0/0/ in 1 hops

41 41 RIP: sending v1 update to via FastEthernet0/0 ( ) RIP: build update entries network metric 2 network metric 1 network metric 1 network metric 2 Directly Connected Learned via RIP from R1 Learned via RIP from R3

42 42 RIP: sending v1 update to via Serial0/0/1 ( ) RIP: build update entries network metric 2 network metric 1 network metric 1 Directly Connected Learned via RIP from R1

43 43 RIP: sending v1 update to via Serial0/0/0 ( ) RIP: build update entries network metric 1 network metric 1 network metric 2 Directly Connected Learned via RIP from R3 R2# undebug all All possible debugging has been turned off

44 44 Does R2 need to send RIP updates out Fa 0/0? What are the disadvantages to this? No, there is no RIP router or any router.  Bandwidth is wasted transporting unnecessary updates.  All devices on the LAN must process the RIPv1 update up to the transport layer.  Security risk (Authentication would is a better solution - later) Passive Interfaces Got Router?

45 45 Passive Interfaces What about using on R2: R2(Config-router)# no network  R2 would not advertise this LAN as a route in updates sent to R1 and R3. Correct solution is to use the passive-interface command Router(config-router)# passive-interface interface-type interface- number

46 46 Passive Interfaces – Use it on R2… R2(config)# router rip R2(config-router)# passive-interface FastEthernet 0/0 X

47 47 Passive Interfaces R2# show ip protocols Interface Send Recv Triggered RIP Key-chain Serial0/0/ Serial0/0/ Automatic network summarization is in effect Routing for Networks: Passive Interface(s): FastEthernet0/0 Routing Information Sources: Gateway Distance Last Update :00: :00:23 Distance: (default is 120) FastEthernet 0/0 no longer included LAN network still included in RIP updates that are sent FastEthernet 0/0 is a passive interface

48 Automatic Summarization Modified Topology B Boundary Routers and Automatic Summarization Processing RIP Updates Sending RIP Updates Advantages and Disadvantages of Automatic Summarization

49 49 Modified Topology: Scenario B Where is the separation of classful networks? Summarizing several routes into a single route is known as route summarization or route aggregation. Fewer routes = smaller routing tables = faster lookups Some routing protocols, such as RIP, automatically summarize routes on certain routers / / /24

50 50 Modified Topology: Scenario B What are the classful networks?  /16  /24  /24 How is /16 network subnetted?  /24  /24  /24 Is /24 subnetted?  / / / /24

51 51 Configuration Changes for R1 R1(config)# interface fa0/0 R1(config-if)# ip address R1(config-if)# interface S0/0/0 R1(config-if)# ip address R1(config-if)# no router rip R1(config)# router rip R1(config-router)# network R1(config-router)# network R1(config-router)# passive-interface FastEthernet 0/0 R1(config-router)# end R1# show run ! router rip passive-interface FastEthernet0/0 network ! IOS automatically corrects subnet entries to classful network address The no shutdown and clock rate commands are not needed because these commands are still configured from Scenario A.

52 52 Configuration Changes for R2 R2(config)# interface S0/0/0 R2(config-if)# ip address R2(config-if)# interface fa0/0 R2(config-if)# ip address R2(config-if)# interface S0/0/1 R2(config-if)# ip address R2(config-if)# no router rip R2(config)# router rip R2(config-router)# network R2(config-router)# network R2(config-router)# passive-interface FastEthernet 0/0 R2(config-router)# end R2# show run ! router rip passive-interface FastEthernet0/0 network network ! IOS automatically corrects subnet entries to classful network address

53 53 Configuration Changes for R3 R3(config)# interface fa0/0 R3(config-if)# ip address R3(config-if)# interface S0/0/1 R3(config-if)# ip address R3(config-if)# no router rip R3(config)# router rip R3(config-router)# network R3(config-router)# network R3(config-router)# passive-interface FastEthernet 0/0 R3(config-router)# end R3# show run ! router rip passive-interface FastEthernet0/0 network network !

54 54 Boundary Routers and Automatic Summarization RIP is a classful routing protocol that automatically summarizes classful networks across major network boundaries.

55 55 Does R2 have interfaces on more than one major classful network?  Yes, and This makes R2 a boundary router in RIP. Boundary routers summarize RIP subnets from one major network to the other:  , , and networks automatically summarized into when sent out R2’s Serial 0/0/1 interface.

56 56 Processing RIP Updates Do Classful routing protocols such as RIPv1 include the subnet mask in the routing update.  No. So how does a router running RIPv1 determine what subnet mask it should apply to a route when adding it to the routing table? R2# show ip route /24 is subnetted, 3 subnets R [120/1] via , 00:00:18, Serial0/0/0 C is directly connected, Serial0/0/0 C is directly connected, FastEthernet0/ /30 is subnetted, 1 subnets C is directly connected, Serial0/0/1 R /24 [120/1] via , 00:00:16, Serial0/0/1

57 57 Rules for Processing RIPv1 Updates The following two rules govern RIPv1 updates:  If a routing update and the interface on which it is received belong to the same major network, the subnet mask of the interface is applied to the network in the routing update.  If a routing update and the interface on which it is received belong to different major networks, the classful subnet mask of the network is applied to the network in the routing update.. Routing Update and Interface Routing Update Subnet Mask Same Classful Major Network Use mask of interface Different Classful Major Network Use default classful mask

58 58 Example of RIPv1 Processing Updates Same classful network as the incoming update. Update: in 1 hops Interface received:  Serial 0/0/ /24 Same classful network address ( ) Applies subnet mask of its S0/0/0 interface, /24. The /24 subnet was added to the routing table. R2# debug ip rip (selected output) RIP: received v1 update from on Serial0/0/ in 1 hops R2# show ip route (selected output) /24 is subnetted, 3 subnets R [120/1] via , 00:00:18, Serial0/0/ /24

59 59 R2# debug ip rip RIP protocol debugging is on RIP: sending v1 update to via Serial0/0/0 ( ) RIP: build update entries network metric 1 network metric 1 network metric 2 RIP: sending v1 update to via Serial0/0/1 ( ) RIP: build update entries network metric 1 Sending RIP Updates / /24

60 60 Sending RIP Updates

61 61 Determining the mask and network address Receiving an Update: Determining subnet mask for routing table  What is the major classful network address of the receiving interface?  What is the major classful network address of the network in the routing update?  Are they the same major classful network address?  Yes: Apply subnet mask of the receiving interface for this network address in the routing table.  No: Apply classful subnet mask for this network address in the routing table. Sending an Update: Determining whether or not to summarize route sent  What is the major classful network address of the sending interface?  What is the major classful network address of the network in the routing update?  Are they the same major classful network address?  Yes: Send subnet network address  No: Send summary address – the classful network address

62 62 Verifying Routing Updates R1# show ip route Gateway of last resort is not set /24 is subnetted, 3 subnets C is directly connected, FastEthernet0/0 C is directly connected, Serial0/0/0 R [120/1] via , 00:00:17, Serial0/0/0 R /24 [120/1] via , 00:00:17, Serial0/0/0 R /24 [120/2] via , 00:00:17, Serial0/0/0 R3# show ip route Gateway of last resort is not set R /16 [120/1] via , 00:00:15, Serial0/0/ /30 is subnetted, 1 subnets C is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0

63 63 Classful routing protocols do not support VLSM Routers running RIPv1 are limited to using the same subnet mask for all subnets with the same classful network. Classless routing protocols such as RIPv2 allow the same major (classful) network to use different subnet masks (VLSM).

64 64 Advantages of Automatic Summarization Smaller routing updates R3# show ip route Gateway of last resort is not set R /16 [120/1] via , 00:00:15, Serial0/0/ /30 is subnetted, 1 subnets C is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0

65 65 Disadvantage of Automatic Summarization Discontiguous network, two or more subnets separated by at least one other major network /16 is a discontiguous network /16

66 66 Discontiguous Networks Do Not Converge with RIPv1 R1(config)# router rip R1(config-router)# network R1(config-router)# network R2(config)# router rip R2(config-router)# network R2(config-router)# network R3(config)# router rip R3(config-router)# network R3(config-router)# network RIPv1 configuration is correct, but it is unable to determine all the networks in this discontiguous topology.

67 67 Discontiguous Networks Do Not Converge with RIPv1 What routing update will be sent by R1 and R3?  major network address, a summary route to R /

68 68 Discontiguous Networks Do Not Converge with RIPv1 R1# show ip route /24 is subnetted, 3 subnets C is directly connected, FastEthernet0/0 C is directly connected, FastEthernet0/1 R3# show ip route /24 is subnetted, 3 subnets C is directly connected, FastEthernet0/0 C is directly connected, FastEthernet0/1 What networks/subnets do you expect to see in R1’s routing table? What networks/subnets do you expect to see in R3’s routing table? Note: The book/curriculum mistakenly has the following routes for R1 and R3 (Book: Figure 5-15 and 5-17). These routes are NOT in the routing tables. R1: R [120/2] via , 00:00:26, Serial0/0/0 R3: R [120/2] via , 00:00:22, Serial0/0/1

69 69 Discontiguous Networks Do Not Converge with RIPv1 R2# show ip route R /16 [120/1] via , 00:00:14, Serial0/0/1 [120/1] via , 00:00:19, Serial0/0/0

70 70 R2 has two equal-cost paths to the network. What will R2 do when it receives traffic for a host on a network ie ?  R2 will load-balance traffic destined for any subnet of  This means that R1 will get half of the traffic and R3 will get the other half of the traffic, whether or not the destination of the traffic is for one of their LANs. R2# show ip route R /16 [120/1] via , 00:00:14, Serial0/0/1 [120/1] via , 00:00:19, Serial0/0/ /16

71 71 Discontiguous Networks Do Not Converge with RIPv1 Classful routing protocols do not support discontiguous networks because they do not include the subnet mask in the routing update. Classless routing protocols (RIPv2, EIGRP, OSPF, IS-IS, BGP) do support discontiguous networks. R2# show ip route R /16 [120/1] via , 00:00:14, Serial0/0/1 [120/1] via , 00:00:19, Serial0/0/0

72 Default Route and RIPv1 Modified Topology C Propagating the Default Route in RIPv1

73 73 Modified Topology: Scenario C Default routes are used by routers to represent all routes that are not specifically in the routing table / / /24

74 74 Default Routes In today’s networks, customers:  Do not necessarily have to exchange routing updates with their ISP.  Do not need a listing for every route on the Internet. Default route that sends all traffic to the ISP router. ISP configures a static route pointing to the customer router for addresses inside the customer’s network.

75 75 Configuration Changes for R2 and R3 R2(config)# router rip R2(config-router)# no network R2(config-router)# exit R2(config)# ip route serial 0/0/1 R3(config)# no router rip R3(config)# ip route serial 0/0/1

76 76 Routing Table R1 has all /24 subnets, but will drop packets for all other networks. No default route (coming) R1# show ip route Gateway of last resort is not set /24 is subnetted, 3 subnets C is directly connected, FastEthernet0/0 C is directly connected, Serial0/0/0 R [120/1] via , 00:00:05, Serial0/0/0

77 77 Routing Table R2 has routes for /16 subnets. R2 has static default route for all other networks R2# show ip route Gateway of last resort is to network /24 is subnetted, 3 subnets R [120/1] via , 00:00:03, Serial0/0/0 C is directly connected, Serial0/0/0 C is directly connected, FastEthernet0/ /30 is subnetted, 1 subnets C is directly connected, Serial0/0/1 S* /0 is directly connected, Serial0/0/1

78 78 Routing Table R3 has static route for /16 network. Doesn’t matter if or how /16 is subnetted, R3 will forward packets to R2. R3# show ip route Gateway of last resort is not set /22 is subnetted, 1 subnets S is directly connected, Serial0/0/ /30 is subnetted, 1 subnets C is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0

79 79 Propagating the Default Route in RIPv1 Can configure static default route on every router but:  inefficient  does not react to topology changes In many routing protocols, including RIP, you can use the default- information originate command in router configuration mode to specify that this router is to originate default information, by propagating the static default route in RIP updates. R1# show ip route Gateway of last resort is not set /24 is subnetted, 3 subnets C is directly connected, FastEthernet0/0 C is directly connected, Serial0/0/0 R [120/1] via , 00:00:05, Serial0/0/0

80 80 Propagating the Default Route in RIPv1 R2(config)# router rip R2(config-router)# default-information originate R2(config-router)# end R2# debug ip rip RIP: sending v1 update to via Serial0/0/0 ( ) RIP: build update entries subnet metric 1 subnet metric 1

81 81 Propagating the Default Route in RIPv1 The static default route on R2 has been propagated to R1 in a RIP update. R1 has connectivity to the LAN on R3 and any destination on the Internet. R1# show ip route * - candidate default, U - per-user static route, o - ODR Gateway of last resort is to network /24 is subnetted, 3 subnets C is directly connected, Serial0/0/0 R [120/1] via , 00:00:16, Serial0/0/0 C is directly connected, FastEthernet0/0 R* /0 [120/1] via , 00:00:16, Serial0/0/0

82 82 Topics RIPv1: Distance Vector, Classful Routing Protocol  Background and Perspective  RIPv1 Characteristics and Message Format  RIP Operation Basic RIPv1 Configuration  RIPv1 Scenario A  Enable RIP: router rip Command  Specifying Networks Verification and Troubleshooting  Verifying RIP: show ip route  Verifying RIP: show ip protocols  Verifying RIP: debu ip rip  Passive Interfaces Automatic Summarization  Modified Topology B  Boundary Routers and Automatic Summarization  Processing RIP Updates  Sending RIP Updates  Advantages and Disadvantages of Automatic Summarization Default Route and RIPv1  Modified Topology C  Propagating the Default Route in RIPv1

83 Chapter 5 RIP version 1 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College Last Updated: 3/10/2009


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