Copyright 2003 CCNA 1 Chapter 8 Routing Fundamentals and Subnets By Joe Parisien
Copyright 2003 Objectives Routed protocol IP routing protocols The mechanics of subnetting
Copyright 2003 Routed Protocols Versus Routing Protocols Routing protocols determine the path that routed protocols follow to their destinations.
Copyright 2003 Characteristics of a Routable Protocol
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.
Copyright 2003 Packet Propagation Each router provides its services to support upper-layer functions.
Copyright 2003 Connectionless Network Services
Copyright 2003 A connection is established between the sender and the recipient before any data is transferred. Connection-Oriented Network Services
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
Copyright 2003 Routing Protocols
Copyright 2003 Router Overview
Copyright 2003 Layer 3 Addresses
Copyright 2003 Routing Versus Switching This distinction is routing and switching use different information in the process of moving data from source to destination.
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.
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.
Copyright 2003 Routing Tables Routers keep track of the following: –Protocol type –Destination/next-hop associations –Routing metric –Outbound interfaces
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
Copyright 2003 RIP and IGRP
Copyright 2003 IGP and EGP IGPs route data within an autonomous system. EGPs route data between autonomous systems.
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)
Copyright 2003 Routing Protocols RIP RIP v2 IGRP EIGRP OSPF IS-IS BGP
Copyright 2003 Mechanics of Subnetting
Copyright 2003 Classes of Network IP Addresses
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.
Copyright 2003 Subnetworks
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.
Copyright 2003 Subnet mask in decimal = Subnet Mask
Copyright 2003 Subnet Addresses
Copyright 2003 Class B address with 8 bits borrowed for the subnet (8 bits borrowed for subnetting) routes to subnet rather than just to network Determining Subnet Mask Size
Copyright 2003 The address would be on the subnet Network FieldSN Host Field Class C address with a subnet mask of (3 bits borrowed) Determining Subnet Mask Size
Copyright 2003 Subnetting Example with AND Operation