1. www.ciscopress.com Copyright 2003 CCNA 1 Chapter 8 Routing Fundamentals and Subnets By Joe Parisien

2. www.ciscopress.com Copyright 2003 Objectives Routed protocol IP routing protocols The mechanics of subnetting

3. www.ciscopress.com Copyright 2003 Routed Protocols Versus Routing Protocols Routing protocols determine the path that routed protocols follow to their destinations.

4. www.ciscopress.com Copyright 2003 Characteristics of a Routable Protocol

5. www.ciscopress.com Copyright 2003 IP as a Routed Protocol IP is a connectionless, unreliable, best-effort delivery protocol. As information flows down the layers of the OSI model; the data is processed at each layer. IP accepts whatever data is passed down to it from the upper layers.

6. www.ciscopress.com Copyright 2003 Packet Propagation Each router provides its services to support upper-layer functions.

7. www.ciscopress.com Copyright 2003 Connectionless Network Services

8. www.ciscopress.com Copyright 2003 A connection is established between the sender and the recipient before any data is transferred. Connection-Oriented Network Services

9. www.ciscopress.com Copyright 2003 Anatomy of an IP Packet Version IP header length (HLEN) Type-of-service Total length Identification Flags Fragment offset Time-to-live Protocol Header checksum Source address Destination address Options Padding Data

10. www.ciscopress.com Copyright 2003 Routing Protocols

11. www.ciscopress.com Copyright 2003 Router Overview

12. www.ciscopress.com Copyright 2003 Layer 3 Addresses

13. www.ciscopress.com Copyright 2003 Routing Versus Switching This distinction is routing and switching use different information in the process of moving data from source to destination.

14. www.ciscopress.com Copyright 2003 Routed Versus Routing A routed protocol: –Includes any network protocol suite that provides enough information in its network layer address to allow a router to forward it to the next device and ultimately to its destination. –Defines the format and use of the fields within a packet. A routing protocol: –Provides processes for sharing route information. –Allows routers to communicate with other routers to update and maintain the routing tables.

15. www.ciscopress.com Copyright 2003 Path Determination Path determination enables a router to compare the destination address to the available routes in its routing table, and to select the best path.

16. www.ciscopress.com Copyright 2003 Routing Tables Routers keep track of the following: –Protocol type –Destination/next-hop associations –Routing metric –Outbound interfaces

17. www.ciscopress.com Copyright 2003 Routing Algorithms and Metrics Routing protocols have one or more of the following design goals: –Optimization –Simplicity and low overhead –Robustness and stability –Flexibility –Rapid convergence Metrics most commonly used by routing protocols include the following: –Bandwidth –Delay –Load –Reliability –Hop count –Ticks –Cost

18. www.ciscopress.com Copyright 2003 RIP and IGRP

19. www.ciscopress.com Copyright 2003 IGP and EGP IGPs route data within an autonomous system. EGPs route data between autonomous systems.

20. www.ciscopress.com Copyright 2003 Link State and Distance Vector Examples of distance-vector protocols: –Routing Information Protocol (RIP) –Interior Gateway Routing Protocol (IGRP) –Enhanced IGRP (EIGRP) Examples of link-state protocols: –Open Shortest Path First (OSPF) –Intermediate System-to-Intermediate System (IS-IS)

21. www.ciscopress.com Copyright 2003 Routing Protocols RIP RIP v2 IGRP EIGRP OSPF IS-IS BGP

22. www.ciscopress.com Copyright 2003 Mechanics of Subnetting

23. www.ciscopress.com Copyright 2003 Classes of Network IP Addresses

24. www.ciscopress.com Copyright 2003 Subnetworks To create a subnet address, a network administrator borrows bits from the original host portion and designates them as the subnet field.

25. www.ciscopress.com Copyright 2003 Subnetworks

26. www.ciscopress.com Copyright 2003 Subnet Mask Determines which part of an IP address is the network field and which part is the host field. Follow these steps to determine the subnet mask: 1. Express the subnetwork IP address in binary form. 2. Replace the network and subnet portion of the address with all 1s. 3. Replace the host portion of the address with all 0s. 4. Convert the binary expression back to dotted-decimal notation.

27. www.ciscopress.com Copyright 2003 Subnet mask in decimal = 255.255.240.0 Subnet Mask

28. www.ciscopress.com Copyright 2003 Subnet Addresses

29. www.ciscopress.com Copyright 2003 Class B address with 8 bits borrowed for the subnet 130.5.2.144 (8 bits borrowed for subnetting) routes to subnet 130.5.2.0 rather than just to network 130.5.0.0. Determining Subnet Mask Size

30. www.ciscopress.com Copyright 2003 The address 197.15.22.131 would be on the subnet 197.15.22.128. 11000101000011110001011010000011 Network FieldSN Host Field Class C address 197.15.22.131 with a subnet mask of 255.255.255.224 (3 bits borrowed) Determining Subnet Mask Size

31. www.ciscopress.com Copyright 2003 Subnetting Example with AND Operation