Notes: If you see any mistake on my PowerPointslides or if you have any questions about thematerials, please feel free to email me firstname.lastname@example.orgThanksVivek KumarTechnicalTrainer
Objectives Encounter and describe the limitations ofRIPv1’s limitations. Apply the basic Routing Information ProtocolVersion 2 (RIPv2) configuration commandsand evaluate RIPv2 classless routing updates. Analyze router output to see RIPv2 support forVLSM and CIDR Identify RIPv2 verification commands andcommon RIPv2 issues. Configure, verify, and troubleshoot RIPv2 in“hands-on” labs
Introduction Difference between RIPv1 & RIPv2RIPv1• A classful distance vector routing protocol• Does not support discontiguous subnets• Does not supportVLSM• Does not send subnet mask in routing update• Routing updates are broadcastRIPv2• A classless distance vector routing protocol that is an enhancementof RIPv1’s features.• Next hop address is included in updates• Routing updates are multicast (18.104.22.168 vs. 255.255.255.255)• The use of authentication is an optionhttp://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/rip.htm
Introduction Similarities between RIPv1 & RIPv2– Use of timers to prevent routing loops– Use of split horizon or split horizon with poisonreverse to also help prevent routing loops.– Use of triggered updates when there is a change in thetopology for faster convergence.– Maximum hop count of 15, with the hop count of 16signifying an unreachable network.
RIPv1 Limitations LabTopology3 router set upTopology is discontiguousThere exists a static summary routeStatic route information can beinjected into routing table updatesusing redistribution.Routers 1 & 3 containVLSM networksRemember that both the R1 and R3routers have subnets that are part ofthe 172.30.0.0/16 major classfulnetwork (class B).Also remember that R1 and R3 areconnected to R2 using subnets of the22.214.171.124/24 major classfulnetwork (class C).This topology is discontiguous andwill not converge because172.30.0.0/16 is divided by the126.96.36.199/24.
RIPv1 Limitations The topology showsthat R2 has a staticsummary route to the192.168.0.0/16 network.The configuration ofthis summary route willbe displayed later in thissection.
RIPv1 Limitations Review theVLSM addressingscheme in the figure. As shown inthe top chart, both R1 and R3have had the 172.30.0.0/16network subnetted into /24subnets.–Four of these /24 subnets areassigned:–two to R1 (172.30.1.0/24 and172.30.2.0/24)–two to R3 (172.30.100.0/24 and172.30.110.0/24). In the bottom chart, we havetaken the 172.30.200.0/24 subnetand subnetted it again, using thefirst four bits for subnets and thelast four bits for hosts.The resultis a 255.255.255.240 mask or /28.Subnet 1 and Subnet 2 areassigned to R3.
RIPv1 Limitations Scenario Continued VLSM-Recall this is sub netting thesubnet Private IP addresses are onLAN links Public IP addresses are usedonWAN links (through an ISP,or when inside users need toaccess outside sites, a publicIP address must be used.) Loopback interfaces-These are virtual interfacesthat can be pinged and addedto routing tableCisco has set these addresses aside for educational purposes.
RIPv1 Limitations Loopback interfacesNotice that R3 is using loopback interfaces (Lo0, Lo1,and Lo2).A loopback interface is a software-only interface thatis used to emulate a physical interface. Like other interfaces, it can be assigned an IP address.Loopback interfaces are also used by other routingprotocols, such as OSPF, for different purposes. These uses will be discussed in Chapter 11 OSPF.In a lab environment, loopback interfaces are useful increating additional networks without having to addmore physical interfaces on the router.A loopback interface can be pinged and the subnet canbe advertised in routing updates.Therefore, loopback interfaces are ideal for simulatingmultiple networks attached to the same router.In our example, R3 does not need four LAN interfacesto demonstrate multiple subnets andVLSM. Instead,we use loopback interfaces.
RIPv1 Limitations Route redistribution– Redistribution involves taking the routes from one routingsource and sending those routes to another routing source.• In our example topology, we want the RIP process on R2 to redistributeour static route (192.168.0.0/16) by importing the route into RIP andthen sending it to R1 and R3 using the RIP process.-R2(config-router)#redistribute static
RIPv1 Limitations R2(config)#ip route 192.168.0.0 255.255.0.0Null0–The address space represented by the static summaryroute 192.168.0.0/16 does not actually exist.–In order to simulate this static route, we use a nullinterface as the exit interface.– You do not need to enter any commands to create orconfigure the null interface.–It is always up but does not forward or receive traffic.Traffic sent to the null interface is discarded.
Static routes and nullinterfaces Static routes and null interfacesR2(config)#ip route 192.168.0.0 255.255.0.0 Null0a static route must have an active exit interface beforeit will be installed in the routing table.Using the null interface will allow R2 to advertise thestatic route in RIP even though networks belonging tothe summary 192.168.0.0/16 do not actually exist.
Verifying and TestingConnectivity show ip interfaces brief–To test whether or not the topology has fullconnectivity, we first verify that both seriallinks on R2 are up using the show ip interfacebrief PingWhenever R2 pings any of the 172.30.0.0 subnetson R1 or R3, only about 50% of the ICMP aresuccessful.R1 is able to ping 10.1.0.1 but is unsuccessful whenattempting to ping the 172.30.100.1 on R3R3 is able to ping 10.1.0.1 but is unsuccessful whenattempting to ping the 172.30.1.1 on R1.
RIPv1 Limitations RIPv1 – a classful routing protocol–Subnet mask are not sent in updates–Summarizes networks at major network boundaries–RIPv1 cannot support discontiguous networks,VLSM, or CIDR.–if network is discontiguous and RIPv1 configured convergence will not bereached–RIPv1 on both the R1 and R3 routers will summarize their 172.30.0.0 subnetsto the classful major network address of 172.30.0.0 when sending routingupdates to R2.–From the perspective of R2, both updates have an equal cost of 1 hop to reachnetwork 172.30.0.0/16. As you will see, R2 installs both paths in the routingtable.
RIPv1 LimitationsExamining the routing tables-To examine thecontents of routingupdates use the debugip rip commandR2 is receiving two 172.30.0.0 equal costroutes with a metric of 1 hop. R2 isreceiving one route on Serial 0/0/0 from R1and the other route on Serial 0/0/1 from R3.R2 has two equal cost routes to the172.30.0.0/16 network.
RIPv1 Limitations•R1 has its own 172.30.0.0 routes:172.30.2.0/24 and 172.30.1.0/24.•But R1 does not send R2 those subnets.•R3 has a similar routing table.•Both R1 and R3 are boundary routers andare only sending the summarized172.30.0.0 network to R2 in their RIPv1routing updates.•As a result, R2 only knows about the172.30.0.0/16 classful network and isunaware of any 172.30.0.0 subnets.•R2 that it is not including the 172.30.0.0 networkin its updates to either R1 or R3.•Because the split horizon rule is in effect.•R2 learned about 172.30.0.0/16 on both theSerial 0/0/0 and Serial 0/0/1 interfaces, it does notinclude that network in updates it sends out thesesame interfaces.
RIPv1 Limitations Because RIPv1 does not send thesubnet mask in routing updates, itcannot supportVLSM. R3 router is configured withVLSMsubnets, all of which are members ofthe class B network 172.30.0.0/16:–172.30.100.0/24 (FastEthernet 0/0)–172.30.110.0/24 (Loopback 0)–172.30.200.16/28 (Loopback 1)–172.30.200.32/28 (Loopback 2) As we saw with the 172.30.0.0/16updates to R2 by R3,–RIPv1 either summarizes thesubnets to the classful boundary–or uses the subnet mask of theoutgoing interface to determinewhich subnets to advertise.R4 is added tothe topologyconnected to R3
RIPv1 Limitations Why is RIPv1 on R3 not including theother subnets, 172.30.200.16/28 and172.30.200.32/28, in updates to R4?– Those subnets do not have the samesubnet mask as FastEthernet 0/0.– R3 will only include those 172.30.0.0routes in its routing table with thesame mask as the exit interface.– Since the interface is 172.30.100.1with a /24 mask, it will only include172.30.0.0 subnets with a /24 mask.The only one that meets thiscondition is 172.30.110.0.– The other 172.30.0.0 subnets,172.30.200.16/28 and172.30.200.32/28, are not includedbecause the /28 masks do not matchthe /24 mask of the outgoinginterface.R4 is added tothe topologyconnected to R3
RIPv1 Limitations No CIDR SupportR2(config)#ip route 192.168.0.025188.8.131.52 Null0–the static route is included inR2s routing table, but R2 willnot include the static route in itsupdate–R1 is not receiving this192.168.0.0/16 route in its RIPupdates from R2, Reason: Classful routingprotocols do not supportCIDR routes that aresummarized with a smallermask than the classfulsubnet mask–If the 192.168.0.0 static routewere configured with a /24 maskor greater, this route would beincluded in the RIP updates.
Configuring RIPv2 Comparing RIPv1 & RIPv2 Message Formats–RIPv2 Message format is similar to RIPv1 but has 2 extensions1st extension is the subnet mask fieldallows a 32 bit mask to be included in the RIP route entry.the receiving router no longer depends upon the subnet mask of the inboundinterface or the classful mask when determining the subnet mask for a route2nd extension is the addition of next hop addressThe Next Hop address is used to identify a better next-hop address - if one exists -than the address of the sending router.If the field is set to all zeros (0.0.0.0), the address of the sending router is the bestnext-hop address.
Configuring RIPv2 Enabling andVerifying RIPv2 Configuring RIP on a Cisco router–By default it is running RIPv1–Even though the router only sends RIPv1messages, it can interpret both RIPv1 and RIPv2messages.–A RIPv1 router will just ignore the RIPv2 fields inthe route entry.RIPv1 RIPv2
Configuring RIPv2 Configuring RIPv2 ona Cisco router-Requires using theversion 2 command-RIPv2 ignores RIPv1updates To verify RIPv2 isconfigured use theshow ip protocolscommand
Comparing RIP v1 and v2 RIP v2 send and receive v2 RIP v1 send v1 but can receive both v1 and v2Version 1 Version 2No. I can nottake version 1Yes. I cantake version 1or 2I can only sendversion 1I can only sendversion 2RIP network is broken
POP Quiz How do you make the RIPv2 back to the default “send 1” and receive 1 or2”? - Hint: Gad(config-router)#version 1 is not the answer.Version 1 Version 2
Configuring RIPv2 Auto-Summary &RIPv2 RIPv2 willautomaticallysummarize routes atmajor networkboundaries and canalso summarize routeswith a subnet maskthat is smaller thanthe classful subnet
Configuring RIPv2 Disabling Auto-Summary in RIPv2 To disableautomaticsummarizationissue the no auto-summarycommand
Configuring RIPv2 Verifying RIPv2 Updates When using RIPv2 with automatic summarizationturned offEach subnet and mask has its own specific entry,along with the exit interface and next-hopaddress to reach that subnet. To verify information being sent by RIPv2 use thedebug ip rip command
VLSM & CIDR RIPv2 andVLSM Networks using aVLSM IP addressingschemeUse classlessrouting protocols (i.e.RIPv2) todisseminatenetwork addressesand their subnet
VLSM & CIDR CIDR uses SupernettingSupernetting is a bunch of contiguousclassful networks that is addressed asa single network.
VLSM & CIDR To verify thatsupernets arebeing sent andreceived use thefollowingcommands-Show iproute-Debug ip rip
Verifying & TroubleshootingRIPv2 BasicTroubleshooting steps-Check the status of all links-Check cabling-Check IP address & subnet maskconfiguration-Remove any unneeded configurationcommands Commands used to verify proper operation ofRIPv2–Show ip interfaces brief–Show ip protocols
Verifying & TroubleshootingRIPv2 Common RIPv2 Issues When trouble shooting RIPv2 examine the following issues: VersionCheck to make sure you are using version 2 Network statementsNetwork statements may be incorrectly typedor missing Automatic summarizationIf summarized routes are not needed then disableautomatic summarization
Verifying & TroubleshootingRIPv2 Reasons why it’s good to authenticate routing information-Prevent the possibility of accepting invalid routing updates-Contents of routing updates are encrypted Types of routing protocols that can use authentication-RIPv2-EIGRP-OSPF-IS-IS-BGP
SummaryRoutingProtocolDistanceVectorClasslessRoutingProtocolUsesHold-DownTimersUse ofSplitHorizonorSplitHorizonw/PoisonReverseMaxHopcount= 15AutoSummarySupportCIDRSupportsVLSMUsesAuthen-ticationRIPv1 Yes No Yes Yes Yes Yes No No NoRIPv2 Yes Yes Yes Yes Yes Yes Yes Yes Yes