CCE1030 Computer Networking

1. CCE1030 Computer Networking Lecture 20 Routing Information Protocol RIPv2 UsamaArusi CCE1030 Usama Arusi

2. Objectives • limitations of RIPv1’s limitations. • Apply the basic Routing Information Protocol Version 2 (RIPv2) configuration commands and evaluate RIPv2 classless routing updates. • Analyze router output to see RIPv2 support for VLSM and CIDR • Identify RIPv2 verification commands and common RIPv2 issues CCE1030 Usama Arusi

3. Content • RIPv1 vs RIPv2. • RIPv1 Limitations. • Configuring RIPv2. • RIPv2 & VLSM. • Verifying and Troubleshooting RIPv2. CCE1030 Usama Arusi

4. Difference between RIPv1 & RIPv2 • RIPv1 • A classful distance vector routing protocol • Does not support discontinuous subnets • Does not support VLSM • Does not send subnet mask in routing update • Routing updates are broadcast • RIPv2 • A classless distance vector routing protocol that is an enhancement of RIPv1’s features • Next hop address is included in updates • Routing updates are multicast (224.0.0.9 vs. 255.255.255.255) • The use of authentication is an option CCE1030 Usama Arusi

5. Similarities between RIPv1 & RIPv2 • Use of timers to prevent routing loops • Use of split horizon or split horizon with poison reverse • Use of triggered updates when there is a change in the topology for faster convergence. • Maximum hop count of 15 , with the hop count of 16 signifying an unreachable network. CCE1030 Usama Arusi

6. RIPv1 Limitations • Lab Topology • 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 • Remember that both the R1 and R3 routers have subnets that are part of the 172.30.0.0/16 major classful network (class B). • Also remember that R1 and R3 are connected to R2 using subnets of the 209.165.200.0/24 major classful network (class C). • This topology is discontiguous and will not converge because 172.30.0.0/16 is divided by the 209.165.200.0/24. CCE1030 Usama Arusi

7. RIPv1 Limitations • Scenario Continued • VLSM -Recall this is sub netting the subnet • Private IP addresses are on LAN links • Public IP addresses are used on WAN links • Loopback interfaces -These are virtual interfaces that can be pinged and added to routing table

8. RIPv1 Limitations • Null Interfaces • This is a virtual interface that does not need to be created or configured -Traffic sent to a null interface is discarded -Null interfaces do not send or receive traffic • Static routes and null interfaces • null interfaces will serve as the exit interface for static route -Example of configuring a static supernet route with a null interface -R2(config)#ip route 192.168.0.0 255.255.0.0 Null0

9. RIPv1 Limitations • Route redistribution -Redistribution involves taking the routes from one routing source and sending those routes to another routing source. • In our example topology, we want the RIP process on R2 to redistribute our static route (192.168.0.0/16) by importing the route into RIP and then sending it to R1 and R3 using the RIP process. -Example : R2(config-router)#redistribute static

10. Verifying and Testing Connectivity • show ip interfaces brief • To test whether or not the topology has full connectivity, we first verify that both serial links on R2 are up using the show ip interface brief • Ping • Whenever R2 pings any of the 172.30.0.0 subnets on R1 or R3, only about 50% of the ICMP are successful. • R1 is able to ping 10.1.0.1 but is unsuccessful when attempting to ping the 172.30.100.1 on R3 • R3 is able to ping 10.1.0.1 but is unsuccessful when attempting to ping the 172.30.1.1 on R1.

11. 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 be reached • RIPv1 on both the R1 and R3 routers will summarize their 172.30.0.0 subnets to the classful major network address of 172.30.0.0 when sending routing updates to R2. • From the perspective of R2, both updates have an equal cost of 1 hop to reach network 172.30.0.0/16. As you will see, R2 installs both paths in the routing table.

12. RIPv1 Limitations • Examining the routing tables To examine the contents of routing updates use the debug ip rip command R2 is receiving two 172.30.0.0 equal cost routes with a metric of 1 hop. R2 is receiving one route on Serial 0/0/0 from R1 and the other route on Serial 0/0/1 from R3. R2 has two equal cost routes to the 172.30.0.0/16 network.

13. RIPv1 Limitations • Because RIPv1 does not send the subnet mask in routing updates, it cannot support VLSM. • R3 router is configured with VLSM subnets, all of which are members of the 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 172.30.0.0/16 updates to R2 by R3, • RIPv1 either summarizes the subnets to the classful boundary • oruses the subnet mask of the outgoing interface to determine which subnets to advertise. R4 is added to the topology connected to R3

14. RIPv1 Limitations • Why is RIPv1 on R3 not including the other subnets, 172.30.200.16/28 and 172.30.200.32/28, in updates to R4? • Those subnets do not have the same subnet mask as FastEthernet 0/0. • R3 will only include those 172.30.0.0 routes in its routing table with the same mask as the exit interface. • Since the interface is 172.30.100.1 with a /24 mask, it will only include 172.30.0.0 subnets with a /24 mask. The only one that meets this condition is 172.30.110.0. • The other 172.30.0.0 subnets, 172.30.200.16/28 and 172.30.200.32/28, are not included because the /28 masks do not match the /24 mask of the outgoing interface. R4 is added to the topology connected to R3

15. RIPv1 Limitations • No CIDR Support • R2(config)#ip route 192.168.0.0 255.255.0.0 Null0 • the static route is included in R2's routing table, but R2 will not include the static route in its update • R1 is not receiving this 192.168.0.0/16 route in its RIP updates from R2, • Reason: Classful routing protocols do not support CIDR routes that are summarized with a smaller mask than the classful subnet mask • If the 192.168.0.0 static route were configured with a /24 mask or greater, this route would be included in the RIP updates.

16. Configuring RIPv2 • Comparing RIPv1 & RIPv2 Message Formats • RIPv2 Message format is similar to RIPv1 but has 2 extensions 1st extension is the subnet mask field • allows a 32 bit mask to be included in the RIP route entry. • the receiving router no longer depends upon the subnet mask of the inbound interface or the classful mask when determining the subnet mask for a route 2nd extension is the addition of next hop address • The 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 best next-hop address.

17. Configuring RIPv2 • Enabling and Verifying RIPv2 • Configuring RIP on a Cisco router • By default it is runningRIPv1 • Even though the router only sends RIPv1 messages, it can interpret both RIPv1 and RIPv2 messages. • A RIPv1 router will just ignore the RIPv2 fields in the route entry. RIPv2 RIPv1

18. Configuring RIPv2 • Configuring RIPv2 on a Cisco router -Requires using the version 2 command -RIPv2 ignores RIPv1 updates • To verify RIPv2 is configured use the show ip protocols command

19. Configuring RIPv2 • Auto-Summary & RIPv2 • 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

20. Configuring RIPv2 • Disabling Auto-Summary in RIPv2 • To disable automatic summarization issue the no auto-summary command

21. Configuring RIPv2 • Verifying RIPv2 Updates • 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. • To verify information being sent by RIPv2 use the debug ip rip command

22. VLSM & CIDR • RIPv2 and VLSM • Networks using a VLSM IP addressing scheme Use classless routing protocols (i.e. RIPv2) to disseminate network addresses and their subnet masks

23. VLSM & CIDR • CIDR uses Supernetting Supernetting is a bunch of contiguous classful networks that is addressed as a single network.

24. VLSM & CIDR • To verify that supernets are being sent and received use the following commands -Show ip route -Debug ip rip

25. Verifying & Troubleshooting RIPv2 • Basic Troubleshooting steps -Check the status of all links -Check cabling -Check IP address & subnet mask configuration -Remove any unneeded configuration commands • Commands used to verify proper operation of RIPv2 • Show ip interfaces brief • Show ip protocols • Debug ip rip • Show ip route

26. Verifying & Troubleshooting RIPv2 • Common RIPv2 Issues • When trouble shooting RIPv2 examine the following 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

27. Summary