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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: - RIP routing is configured
- The
correct interfaces are sending and receiving RIP updates
- The router is advertising the correct networks
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: - show interface
interface
- show ip interface
interface
- show running-config
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
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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: - show ip rip database
- show ip
protocols {summary}
- show ip route
- debug ip rip {events}
- show ip interface
brief
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
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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