© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 RIP version 1 Routing Protocols and Concepts – Chapter 5 Modified by Tony Chen 06/10/2008

ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Notes:  If you see any mistake on my PowerPoint slides or if you have any questions about the materials, please feel free to me at Thanks! Tony Chen College of DuPage Cisco Networking Academy

ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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 IPv6 form of RIP called RIPng (next generation) is now available

ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public RIPv1  Administrative Distance –RIP’s default administrative distance is 120

ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Basic RIPv1 Configuration  Router RIP Command –To enable RIP enter: - Router rip at the global configuration prompt -Prompt will look like R1(config-router)#

ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Verification and Troubleshooting  Show ip Route  To verify and troubleshoot routing - Use the following commands: -show ip route -show ip protocols -debug ip rip

ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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”?

ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Verification and Troubleshooting  Debug ip rip command -Used to display RIP routing updates as they are happening

ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Verification and Troubleshooting  Passive interfaces

ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Preventing routing updates through an interface  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. Lab:

ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Preventing routing updates through an interface  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. It will break the rip update You can use the “ip route” command to send route update back to establish the 2 way communication 1 2

ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Automatic Summarization Modified Topology  The original scenario has been modified such that: Three classful networks are used: / / /24 The /16 network is subnetted into three subnets: / / /24 The following devices are part of the /16 classful network address: All interfaces on R1 S0/0/0 and Fa0/0 on R

ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Automatic Summarization  Boundary Routers –RIP automatically summarizes classful networks –Boundary routers summarize RIP subnets from one major network to another.

ITE PC v4.0 Chapter 1 24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Automatic Summarization  Sending RIP Updates –RIP uses automatic summarization to reduce the size of a routing table.

ITE PC v4.0 Chapter 1 26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Automatic Summarization  Disadvantage of Automatic Summarization: -Does not support discontiguous networks

ITE PC v4.0 Chapter 1 28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Automatic Summarization

ITE PC v4.0 Chapter 1 30 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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 s0/0/1

ITE PC v4.0 Chapter 1 31 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Default Route and RIPv1

ITE PC v4.0 Chapter 1 32 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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.

ITE PC v4.0 Chapter 1 33 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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 /24 [120/1] via , 00:00:11, Serial0 R /24 [120/1] via , 00:00:11, Serial0 C /24 is directly connected, Serial0 C /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 /24 [120/1] via , 00:00:04, Serial0 C /24 is directly connected, Ethernet0 C /24 is directly connected, Serial0 R /24 [120/1] via , 00:00:04, Serial0 R /24 [120/2] via , 00:00:04, Serial0 Centre(config)#ip route loopback0 Setup up a default route on the Centre router Centre(config)#router rip Centre(config-router)#default-information originate Centre#sh ip route Codes: C - connected, S - static, * - candidate default Gateway of last resort is to network C is directly connected, Loopback0 R /24 [100/8576] via , 00:00:22, Serial0 R /24 [120/2] via , 00:00:22, Serial0 S* /0 is directly connected, Loopback0 Mobile#sho ip route Codes: C - connected, S - static, * - candidate default - RIP, Gateway of last resort is to network R /24 [120/1] via , 00:00:09, Serial0 C /24 is directly connected, Ethernet0 C /24 is directly connected, Serial0 R /24 [120/1] via , 00:00:04, Serial0 R /24 [120/2] via , 00:00:09, Serial0 R* /0 [120/2] via , 00:00:09, Serial0

ITE PC v4.0 Chapter 1 34 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 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

ITE PC v4.0 Chapter 1 35 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary: Commands used by RIP CommandCommand’s purpose Rtr(config)#router ripEnables RIP routing process Rtr(config-router)#networkAssociates a network with a RIP routing process Rtr#debug ip ripused to view real time RIP routing updates Rtr(config-router)#passive-interface fa0/0Prevent RIP updates from going out an interface Rtr(config-router)#default-information originateUsed by RIP to propagate default routes Rtr#show ip protocolsUsed to display timers used by RIP

ITE PC v4.0 Chapter 1 36 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public