© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 RIP version 1&2 Revised by Chakchai So-In, Ph.D.

ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Agenda  History of RIP (v1, v2, ng)  RIPv1 Encapsulation and message format  RIPv1 Operation and Configuration  RIPv1 Verification and Troubleshooting  RIPv1 vs. RIPv2  RIPv1 Limitation  RIPv2 Configuration  RIPv2 Verification and Troubleshooting  Summary

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

ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public RIPv1 (Characteristics) -A classful, Distance Vector (DV) routing protocol -Class A : ( ) -Class B : ( ) -Class C : ( ) -Does not send subnet masks in routing updates -Metric = hop count -Routes with a hop count > 15 are unreachable -Updates are broadcast every 30 seconds

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  Encapsulated RIPv1 Message -Frame Header : Broadcast (MAC Dest.) / Sending Interface (Src.) RIPv1 (Encapsulated Message)

 RIP Message Format  RIP header - divided into 3 fields -Command field -Version field -Must be zero  Route Entry - composed of 3 fields -Address family identifier -IP address -Metric RIPv1 (RIPv1 Message)

ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public -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 Click here to show animation RIPv1 Operation (2 message types)

ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public RIP : Example Destination Network Next Router Num. of hops to dest. wA2 yB2 zB7 x--1 ….…..... w xy z A C D B Routing/Forwarding table in D

ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public RIP : Example (cont.) Destination Network Next Router Num. of hops to Dest. wA2 yB2 zB A7 5 x--1 ….…..... Routing/Forwarding table in D w xy z A C D B Dest Next hops w - 1 x - 1 z C 4 …. …... Advertisement from A to D

RIPv1 (Administrative Distance – AD) RIPv2 AD = 120

RIPv1 (Simple Configuration) RIPv2 AD = Subnets + 3 Routers To enable RIP enter: -Router rip at the global configuration prompt -Prompt will look like R1(config-router)# Specifying Networks -Use the network command to: -Enable RIP on all interfaces -Advertise this network in RIP updates

RIPv1 (Verification & Troubleshooting) Commands: #show ip route #debug ip rip #show ip protocols

RIPv1 (Verification & Troubleshooting) cont. Commands: #show ip route #debug ip rip #show ip protocols

ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public -Used to prevent a router from sending updates through an interface -Example: Router(config- router)#passive-interface interface-type interface- number RIPv1 (Passive Interface)

RIPv1 (Automatic Route Summarization - ASR) Boundary Routers: -RIP automatically summarizes classful networks -Boundary routers summarize RIP subnets from one major network to another. Modified Scenario: -Three classful networks are used: / / /24 -The /16 network is subnetted into three subnets: / / /24

RIPv1 (ASR) 2 rules govern RIPv1 updates: -If a routing update and the interface it’s received on belong to the same network (match subnet mask) 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 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public -Advantages : -The size of routing updates is reduced. -Single routes are used to represent multiple routes. which results in faster lookup in the routing table. -Disadvantages: -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. RIPv1 (Automatic Route Summarization)

Default Route Command: #ip route s0/0/1 RIPv1 (Default Route)

Route Command: #default-information originate -This command is used to specify that the router is to originate default information, by propagating the static default route in RIP update. RIPv1 (Propagating the Default Route)

ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public RIPv1 vs. RIPv2 (The Difference) -RIPv1 -A classful distance vector routing protocol (DV) -Does not support discontiguous subnets -Does not support VLSM -Does not send subnet mask in routing update -Routing updates are broadcast -RIPv2 -A classless DV -Next hop address is included in updates -Routing updates are multicast -The use of authentication is an option -What is the same? -Use of timers to prevent routing loops -Use of split horizon or split horizon with poison reverse -Use of triggered updates -Maximum hop count of 15

RIPv1 (Limitation - Scenario) Scenario : -3 router set up -Topology is discontiguous -There exists a static summary route. -Static route information can be injected into routing table updates using redistribution. -Routers 1 & 3 contain VLSM networks VLSM (This is sub netting the subnet) -Private IP addresses are on LAN links -Public IP addresses are used on WAN links -Loopback interfaces : LoX (These are virtual interfaces that can be pinged and added to routing table.)

RIPv2 (VLSM Review) -Case I : Both R1 and R3 have had the /16 network subnetted into /24 subnets. Four of these /24 subnets are assigned. -Case II : /24 subnet and subnetted it again, using the first four bits for subnets and the last four bits for hosts. The result is a mask or /28.

RIPv1 (Limitation – RR) Route Redistribution (RR) Command : -Redistribution command is way to disseminate a static route from one router to another via a routing protocol R2(config-router)#redistribute static Verifying/ Testing Connectivity : #show ip interfaces brief #ping #traceroute

RIPv1 (Limitation – no VLSM) No VLSM supported : -RIPv1 does not send subnet mask in routing updates. -RIPv1 does summarize routes to the Classful boundary Or uses the subnet mask of the outgoing interface to determine which subnets to advertise. Example : R3 (VLSM) : class B network / /24 (FastEthernet 0/0) /24 (Loopback 0) /28 (Loopback 1) /28 (Loopback 2)

RIPv1 (Limitation – no CIDR) No CIDR Support : -Classful routing protocols do not support CIDR routes that are summarized with a smaller mask than the classful subnet mask. R2 will not include the static route in its update SO no such route in R1.

RIPv2 (RIPv1 vs. RIPv2 Message) RIPv2 message format is similar to RIPv1 BUT has 2 extensions -1 st extension is the subnet mask field -2 nd extension is the addition of next hop address (identify a better next-hop address - if one exists)

RIPv2 (Configuration) – Cisco Default = RIPv1 To configure RIPv2: -Requires using the version 2 command -RIPv2 ignores RIPv1 updates -To verify RIPv2 is configured: #show ip protocols

RIPv2 (Configuration) – Auto-Summary -RIPv2 will automatically summarize routes at major network boundaries and can also summarize routes with a subnet mask that is smaller than the classful subnet mask.

RIPv2 (Configuration) – no auto-summary When using RIPv2 with automatic summarization turned off, Each subnet and mask has its own specific entry, along with the exit interface and next- hop address to reach that subnet. -Disabling Auto-Summary #no auto-summary -Verifying RIPv2 Updates #debug ip rip

RIPv2 (VLSM) Networks using a VLSM IP addressing scheme : -Use classless routing protocols to disseminate network addresses and their subnet masks

RIPv2 (CIDR) CIDR uses Supernetting : -Supernetting is a bunch of contiguous classful networks that is addressed as a single network. -To verify that supernets are being sent and received #show ip route #debug ip rip

RIPv2 (Verify and Troubleshoot) Basic Troubleshooting Steps: -Check the status of all links -Check cabling -Check IP address & subnet mask configuration -Remove any unneeded configuration commands Common RIPv2 Issues: -Version : Check to make sure you are using version 2 -Network statements : Network statements may be incorrectly typed or missing -Automatic summarization : If summarized routes are not needed then disable automatic summarization Commands used to verify proper operation of RIPv2: #show ip interfaces brief #show ip protocols #debug ip rip #show ip route

ITE PC v4.0 Chapter 1 33 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary Routing Protocol Distance Vector Classless Routing Protocol Uses Hold- Down Timers Use of Split Horizon or Split Horizon w/ Poison Revers e Max Hop count = 15 Auto Summary Suppor t CIDR Support s VLSM Uses Authen - ticatio n RIPv1YesNoYes No RIPv2Yes

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