RIP version 1

1. RIP version 1 Routing Protocols and Concepts – Chapter 5 Modified by Tony Chen 06/10/2008

2. Notes: • If you see any mistake on my PowerPoint slides or if you have any questions about the materials, please feel free to email me at chento@cod.edu. Thanks! Tony Chen College of DuPage Cisco Networking Academy

3. Objectives • Describe the functions, characteristics, and operation of the RIPv1 protocol. • Configure a device for using RIPv1. • Verify proper RIPv1 operation. • Describe how RIPv1 performs automatic summarization. • Configure, verify, and troubleshoot default routes propagated in a routed network implementing RIPv1. • Use recommended techniques to solve problems related to RIPv1

4. RIP Historical Impact • RIP evolved from an earlier protocol developed at Xerox, called Gateway Information Protocol (GWINFO). • With the development of Xerox Network System (XNS), GWINFO evolved into RIP. • It later gained popularity because it was implemented in the Berkeley Software Distribution (BSD) as a daemon named routed (pronounced "route-dee", not "rout-ed"). • Recognizing the need for standardization of the protocol, Charles Hedrick wrote RFC 1058 in 1988, in which he documented the existing protocol and specified some improvements. • Since then, RIP has been improved with RIPv2 in 1994 and with RIPng in 1997. IPv6 form of RIP called RIPng (next generation) is now available

5. RIPv1 • RIP Characteristics • A classful, Distance Vector (DV) routing protocol • Metric = hop count • Routes with a hop count > 15 are unreachable • Updates are broadcast every 30 seconds • The data portion of a RIP message is encapsulated into a UDP segment, with both source and destination port numbers set to 520.

6. RIPv1 • RIP Message Format • RIP header - divided into 3 fields • Command field • REQUEST (1)- Request either a partial or full table update from another RIP router. • RESPONSE (2) - A response to a request. • Version field • 1 or 2 • Must be zero • Must be zero" fields provide room for future expansion of the protocol. • Route Entry - composed of 3 fields • Address family identifier • CLNS, IPX, IP etc. • IP address • Metric

7. RIPv1 • RIP Operation • RIP uses 2 message types: • Request message -This is sent out on startup by each RIP enabled interface -Requests all RIP enabled neighbors to send routing table • Response message -Message sent to requesting router containing routing table

8. RIPv1 • IP addresses initially divided into classes -Class A -Class B -Class C • RIP is a classful routing protocol -Does not send subnet masks in routing updates

9. Common RIP configuration issues RIP and IGRP: • Classful network statements only • IOS will take subnetted networks but will translate it into the classful network for the running-config.

10. RIPv1 • Administrative Distance • RIP’s default administrative distance is 120

11. Basic RIPv1 Configuration • A typical topology suitable for use by RIPv1 includes: • -Three router set up • -No PCs attached to LANs -Use of 5 different IP subnets

12. Basic RIPv1 Configuration • Router RIP Command • To enable RIP enter: • -Router rip at the global configuration prompt • -Prompt will look like R1(config-router)#

13. Basic RIPv1 Configuration • Specifying Networks • Use the network command to: • -Enable RIP on all interfaces that belong to this network • -Advertise this network in RIP updates sent to other routers every 30 seconds

14. Verification and Troubleshooting • Show ip Route • To verify and troubleshoot routing -Use the following commands: -show ip route -show ip protocols -debug ip rip

15. Verification and Troubleshooting • show ip protocols command -Displays routing protocol configured on router POP QUIZ: What is the different between the output of the command “show ip route” and “show ip protocol”?

16. Verification and Troubleshooting • Debug ip rip command -Used to display RIP routing updates as they are happening

17. Verification and Troubleshooting • Passive interface command -Used to prevent a router from sending updates through an interface -Example: Router(config-router)#passive-interface interface-type interface-number

18. Verification and Troubleshooting • Passive interfaces

19. Preventing routing updates through an interface Lab: • Route filtering works by regulating the routes that are entered into or advertised out of a route table. • As a result, a route filter influences which routes the router advertises to its neighbors. • On the other hand, routers running link state protocols determine routes based on information in the link-state database. Route filters have no effect on link-state advertisements or the link-state database. • (Tony) Route filtering could have negative effect on the link-state routing protocol. • Using the passive interface command can prevent routers from sending routing updates through a router interface, but the router continues to listen and use routing updates from that neighbor. • Keeping routing update messages from being sent through a router interface prevents other systems on that network from learning about routes dynamically.

20. Preventing routing updates through an interface It will break the rip update 1 • Again, this is only half the story. • When you use “passive interface” on a distance vector routing protocol, you need to complement it with “ip route” command. You can use the “ip route” command to send route update back to establish the 2 way communication 2

21. Automatic Summarization 172.30.3.0 Modified Topology • The original scenario has been modified such that: Three classful networks are used: 172.30.0.0/16 192.168.4.0/24 192.168.5.0/24 The 172.30.0.0/16 network is subnetted into three subnets: 172.30.1.0/24 172.30.2.0/24 172.30.3.0/24 The following devices are part of the 172.30.0.0/16 classful network address: All interfaces on R1 S0/0/0 and Fa0/0 on R2 172.30.2.0 172.30.1.0

22. Automatic Summarization • Configuration Details -To remove the RIP routing process use the following command No router rip -To check the configuration use the following command Show run

23. Automatic Summarization • Boundary Routers • RIP automatically summarizes classful networks • Boundary routers summarize RIP subnets from one major network to another.

24. Automatic Summarization Processing RIP Updates • 2 rules govern RIPv1 updates: -If a routing update and the interface it’s received on belong to the same network then The subnet mask of the interface is applied to the network in the routing update -If a routing update and the interface it’s received on belong to a different network then The classful subnet mask of the network is applied to the network in the routing update.

25. Automatic Summarization • Sending RIP Updates • RIP uses automatic summarization to reduce the size of a routing table.

26. Automatic Summarization • Advantages of automatic summarization: -The size of routing updates is reduced -Single routes are used to represent multiple routes which results in faster lookup in the routing table.

27. Automatic Summarization • Disadvantage of Automatic Summarization: -Does not support discontiguous networks

28. Automatic Summarization • Discontiguous Topologies do not converge with RIPv1 • A router will only advertise major network addresses out interfaces that do not belong to the advertised route.

29. Automatic Summarization

30. Default Route and RIPv1 • Modified Topology: Scenario C • Default routes • Packets that are not defined specifically in a routing table will go to the specified interface for the default route • Example: Customer routers use default routes to connect to an ISP router. • Command used to configure a default route is • ip route 0.0.0.0 0.0.0.0 s0/0/1

31. Default Route and RIPv1

32. Default Route and RIPv1 • Propagating the Default Route in RIPv1 • Default-information originate command • -This command is used to specify that the router is to originate default information, by propagating the static default route in RIP update.

33. Default route with RIP Centre#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, Gateway of last resort is not set R 192.168.4.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0 R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0 C 192.168.2.0/24 is directly connected, Serial0 C 192.168.3.0/24 is directly connected, Ethernet0 Mobile#sho ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, Gateway of last resort is not set R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0 C 192.168.5.0/24 is directly connected, Ethernet0 C 192.168.1.0/24 is directly connected, Serial0 R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0 R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:04, Serial0 Setup up a default route on the Centre router Centre(config)#ip route 0.0.0.0 0.0.0.0 loopback0 Centre(config)#router rip Centre(config-router)#default-information originate Mobile#sho ip route Codes: C - connected, S - static, * - candidate default - RIP, Gateway of last resort is 192.168.1.1 to network 0.0.0.0 R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:09, Serial0 C 192.168.5.0/24 is directly connected, Ethernet0 C 192.168.1.0/24 is directly connected, Serial0 R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0 R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:09, Serial0 R* 0.0.0.0/0 [120/2] via 192.168.1.1, 00:00:09, Serial0 Centre#sh ip route Codes: C - connected, S - static, * - candidate default Gateway of last resort is 0.0.0.0 to network 0.0.0.0 C 172.16.1.1 is directly connected, Loopback0 R 192.168.4.0/24 [100/8576] via 192.168.2.1, 00:00:22, Serial0 R 192.168.5.0/24 [120/2] via 192.168.2.1, 00:00:22, Serial0 S* 0.0.0.0/0 is directly connected, Loopback0

34. Summary • RIP characteristics include: Classful, distance vector routing protocol Metric is Hop Count Does not support VLSM or discontiguous subnets Updates every 30 seconds • Rip messages are encapsulated in a UDP segment with source and destination ports of 520

35. Summary: Commands used by RIP