Cisco Internetwork Troubleshooting © 2005 Cisco Systems, Inc. All rights reserved. Applying a Layered Model to a Network CIT v5.22-1

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Outline What are the Differences Between the Layered Networking Models? Identifying the Encapsulated Data Flow Process Where Do Network Devices Map in a Logical Model?

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Comparing the OSI Model with the TCP/IP Model

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Comparing the OSI Model with the TCP/IP Model

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Comparing the OSI Model with the TCP/IP Model

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Comparing the OSI Model with the TCP/IP Model

© 2005 Cisco Systems, Inc. All rights reserved. CIT v The Process of Encapsulated Data Flow on a Simple Connection Sending data from an application in End System A to an application in End System B

© 2005 Cisco Systems, Inc. All rights reserved. CIT v The Process of Encapsulated Data Flow on a Simple Connection Sending data from an application in End System A to an application in End System B

© 2005 Cisco Systems, Inc. All rights reserved. CIT v The Process of Encapsulated Data Flow on a Simple Connection Sending data from an application in End System A to an application in End System B

© 2005 Cisco Systems, Inc. All rights reserved. CIT v The Process of Encapsulated Data Flow on a Simple Connection Sending data from an application in End System A to an application in End System B

© 2005 Cisco Systems, Inc. All rights reserved. CIT v The Process of Encapsulated Data Flow on a Simple Connection Sending data from an application in End System A to an application in End System B

© 2005 Cisco Systems, Inc. All rights reserved. CIT v PhysicalData LinkNetworkTransportApplication Network Devices Mapped to a Logical Layered Model Firewall X Standard Switch XX Multilayer Switch X X Hub End System XXX Router XXX X X * * *X X XX

© 2005 Cisco Systems, Inc. All rights reserved. CIT v Summary The TCP/IP networking model maps closely to the layers of the OSI networking model. The ability to identify the stages of the encapsulated data flow process enhances the ability of a troubleshooter to diagnose problems as data moves between points within an end-to-end network. The ability to identify which logical layers a device uses gives a troubleshooter the ability to minimize the complexity of a problem by dividing the problem into manageable parts.