1. CCE1030 Computer Networking
Lecture 19
Routing Information Protocol RIPv1
Usama Arusi
January 2018
CCE1030 Usama Arusi

2. Outcomes
Describe the characteristics, and operation of the RIPv1 protocol
Demonstrate device configuration using RIPv1
Verify proper RIPv1 operation
Describe how RIPv1 performs automatic summarization
Illustrate how to troubleshoot default routes propagated in a routed network implementing RIPv1
January 2018
CCE1030 Usama Arusi

3. Recap: Routing Protocols
Routers are the main devices used to connect networks.
They forward packets in a network from source to destination.
Use forwarding tables.
Entries in forwarding tables can be set manually or automatically.
Routing protocols are used to automatically set forwarding tables.
January 2018
CCE1030 Usama Arusi

4. Recap: Routing Protocols
Routing protocols use a hierarchical structure
Static – manually configured
Dynamic – routing protocols
Dynamic routing consists of routing tables that are built and maintained automatically through an on going communication between routers
Routing protocols grouped according to characteristics
January 2018
CCE1030 Usama Arusi

5. Recap: Routing Protocols
Types of routing protocols:
Interior Gateway Protocols (IGP)
Used for routing inside an autonomous system & used to route within the individual networks themselves
Examples: RIP, EIGRP, OSPF
Exterior Routing Protocols (EGP)
Used for routing between autonomous systems
Example: BGPv4
January 2018
CCE1030 Usama Arusi

6. Recap: Distance Vector routing
One of the two major classes of intra domain routing protocols
Routes are advertised as vectors of (distance, direction), where distance is defined in terms of a metric and direction is defined in terms of the next-hop router
For example:
Destination A is a distance of 5 hops away, in the direction of next-hop router X
January 2018
CCE1030 Usama Arusi

7. Content Characteristics, and operation of the RIPv1 protocol.
Configure a device for using RIPv1.
Verify proper RIPv1 operation.
Automatic summarization.
Configure, verify, and troubleshoot default routes.
January 2018
CCE1030 Usama Arusi

8. RIP Characteristics A classful, Distance Vector (DV) routing protocol
Cost metric = hop count
Each link has a cost of 1
Routes with a hop count > 15 are unreachable
Limiting network size
Updates are broadcast every 30 seconds
Using a RIP response message – containing a list of up to 25 destinations
January 2018
CCE1030 Usama Arusi

9. RIP Operation RIP uses 2 message types: Request message
This is sent out on startup by each RIP enabled interface
Requests all RIP enabled neighbours to send routing table
Response message
Message sent to neighbouring router containing routing table
This message might be a response to a request, or it might be an update message generated by the sender
January 2018
CCE1030 Usama Arusi

10. Forwarding Information Base
RIPv1 protocol keeps the following information about each destination:
IP address—IP address of the destination host or network
Gateway—The first gateway along the path to the destination
Interface—The physical network that must be used to reach the destination
Metric—A number indicating the number of hops to the destination
Timer—The amount of time since the entry was last updated
January 2018
CCE1030 Usama Arusi

11. Subnet Masks in Routing Updates
IP addresses initially divided into classes
Class A
Class B
Class C
RIP is a classful routing protocol
Does not send subnet masks in routing updates
January 2018
CCE1030 Usama Arusi

12. Administrative Distance
Multiple routing protocols may exist on any one given network
Most routing protocols have metric structures and algorithms that are not compatible with other protocols
The exchange of route information and the selection of the best path across the multiple protocols are critical
Administrative distance is the feature that routers use in order to select the best path when there are two or more different routes to the same destination from two different routing protocols
January 2018
CCE1030 Usama Arusi

13. Administrative Distance
Administrative distance defines the reliability of a routing protocol
It is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination
It has only local significance
It is not advertised in routing updates
January 2018
CCE1030 Usama Arusi

14. Administrative Distance
RIP’s default administrative distance is 120
January 2018
CCE1030 Usama Arusi

15. Basic RIPv1 Configuration
A typical topology suitable for use by RIPv1 includes:
Three router set up
No PCs attached to LANs
Use of 5 different IP subnets
January 2018
CCE1030 Usama Arusi

16. Basic RIPv1 Configuration
To activate RIP on the router the protocol stack has to be turned on
To enable RIP enter:
Router rip at the global configuration prompt
Prompt will look like R1(config-router)#
January 2018
CCE1030 Usama Arusi

17. Basic RIPv1 Configuration
Specifying Networks
R1 has 2 directly connected networks
Enable RIP on all interfaces that belong to this network
Advertise this network in RIP updates sent to other routers every 30 seconds
Repeat process for R2 and R3
January 2018
CCE1030 Usama Arusi

18. Verification and Troubleshooting
To verify and troubleshoot routing use the following commands:
show ip route
show ip protocols
debug ip rip
January 2018
CCE1030 Usama Arusi

19. Verification and Troubleshooting
Verify and troubleshoot commands:
show ip route
show ip protocols
Displays routing protocol configured on router
debug ip rip
January 2018
CCE1030 Usama Arusi

20. Verification and Troubleshooting
Verify and troubleshoot commands:
show ip route
show ip protocols
debug ip rip
Used to display RIP routing updates as they are happening
January 2018
CCE1030 Usama Arusi

21. Verification and Troubleshooting
Passive interface command
Used to prevent a router from sending updates through an interface
January 2018
CCE1030 Usama Arusi

22. Automatic Summarization
RIP uses automatic summarization to reduce the size of a routing table
Example:
Three classful networks are used:
/16
/24
/24
The /16 network is
subnetted into three subnets:
/24
/24
/24
January 2018
CCE1030 Usama Arusi

23. Automatic Summarization
Boundary Router
Is a router that has interfaces in more than one major classful network
Boundary routers summarize RIP subnets from one major network to another
January 2018
CCE1030 Usama Arusi

24. Automatic Summarization
Processing RIP Updates
January 2018
CCE1030 Usama Arusi

25. Automatic Summarization
Advantages of automatic summarization:
The size of routing updates is reduced
Single routes are used to represent multiple routes which results in faster lookup in the routing table
Disadvantage of Automatic Summarization:
Does not support discontiguous networks
January 2018
CCE1030 Usama Arusi