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Content 7.2 RIP 7.2.5 Verifying RIP configuration There are several commands that can be used to verify that RIP is properly configured. Two of the most common are the show ip route command and the show ip protocols command.The show ip protocols command shows which routing protocols are carrying IP traffic on the router. This output can be used to verify most if not all of the RIP configuration. Some of the most common configuration items to verify are: The show ip route command can be used to verify that routes received by RIP neighbors are installed in the routing table. Examine the output of the command and look for RIP routes signified by "R". Remember that the network will take some time to converge so the routes may not appear immediately. Additional commands to check RIP configuration are as follows: Lab Activity e-Lab Activity: Verifying RIP Configuration This lab is to use IOS show commands to verify the operation of a router running RIP. Web Links Configuring RIP http://www.cisco.com/en/US/products/sw/ iosswrel/ps1831/ products_configuration_guide_ chapter09186a00800d97f7.html#xtocid1
Content 7.2 RIP 7.2.6 Troubleshooting RIP update issues Most of the RIP configuration errors involve an incorrect network statement, discontiguous subnets, or split horizons. One highly effective command for finding RIP update issues is the debug ip rip command.The debug ip rip command displays RIP routing updates as they are sent and received. The example in Figure shows the output from a router using the debug ip rip command after receiving a RIP update. After receiving and processing the update, the router sends the newly updated information out its two RIP interfaces. The output shows the router is using RIP version 1 and broadcasts the update (broadcast address 255.255.255.255). The number in parenthesis represents the source address encapsulated into the IP header of the RIP update. There are several key indicators to look for in the output of the debug ip rip command. Problems such as discontiguous subnetworks or duplicate networks can be diagnosed with this command. A symptom of these issues would be a router advertising a route with a metric that is less than the metric it received for that network. Other commands to troubleshoot RIP: Lab Activity Lab Exercise: Troubleshooting RIP This lab is to set up an IP addressing scheme using class B networks. Lab Activity e-Lab Activity: Troubleshooting RIP Update Issues This lab is to perform a basic configuration of the router Pretoria. Lab Activity e-Lab Activity: Troubleshooting RIP In this lab, the students will be troubleshooting the Routing Information Protocol on the routers Gadsen and Birmingham. Web Links Configuring RIP http://www.cisco.com/en/US/products/sw/
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Content 7.2 RIP 7.2.7 Preventing routing updates through an interface Route filtering works by regulating the routes that are entered into or advertised out of a route table. These have different effects on link-state routing protocols than they do on distance vector protocols. A router running a distance vector protocol advertises routes based on what is in its 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, rather than the neighboring router advertised route entries. Route filters have no effect on link-state advertisements or the link-state database. For this reason, the information in this document only applies to distance vector IP Routing Protocols such as Routing Information Protocol (RIP), and Interior Gateway Routing Protocol (IGRP). Using the passive interface command can prevent routers from sending routing updates through a router interface. Keeping routing update messages from being sent through a router interface prevents other systems on that network from learning about routes dynamically. Router E uses the command to keep routing updates from being sent. For RIP and IGRP, the passive interface command stops the router from sending updates to a particular neighbor, 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 the interface from learning about routes dynamically. Lab Activity Lab Exercise: Preventing Routing Updates Through an Interface This lab is to prevent routing updates through an interface to regulate advertised routes. Lab Activity e-Lab Activity: Preventing Routing Updates through an Interface In this lab, the students will learn to prevent routing updates through an interface to regulate advertised routes and observe the results.
Content 7.2 RIP 7.2.8 Load balancing with RIP Load balancing is a concept that allows a router to take advantage of multiple best paths to a given destination. These paths are either statically defined by a network administrator or calculated by a dynamic routing protocol such as RIP.RIP is capable of load balancing over as many as six equal-cost paths, with four paths being default. RIP performs what is referred to as “round robin” load balancing. This means that RIP takes turns forwarding packets over the parallel paths. Figure shows an example of RIP routes with four equal cost paths. The router will start with an interface pointer to the interface connected to router 1. Then the interface pointer cycles through the interfaces and routes in a deterministic fashion such as 1-2-3-4-1-2-3-4-1 and so on. Because the metric for RIP is hop count, no regard is given to the speed of the links. Therefore, the 56 Kbps path will be given the same preference as the 155 Mbps path. Equal cost routes can be found by using the show ip route command. For example, Figure is a display of the output show ip route to a particular subnet with multiple routes. Notice there are two routing descriptor