1. Ch.4 – Learning About Other Devices (CDP and Telnet) CCNA 1 version 3.0 Rick Graziani Cabrillo College

2. Rick Graziani graziani@cabrillo.edu2 Note to instructors If you have downloaded this presentation from the Cisco Networking Academy Community FTP Center, this may not be my latest version of this PowerPoint. For the latest PowerPoints for all my CCNA, CCNP, and Wireless classes, please go to my web site: http://www.cabrillo.cc.ca.us/~rgraziani/ The username is cisco and the password is perlman for all of my materials. If you have any questions on any of my materials or the curriculum, please feel free to email me at graziani@cabrillo.edu (I really don’t mind helping.) Also, if you run across any typos or errors in my presentations, please let me know. I will add “(Updated – date)” next to each presentation on my web site that has been updated since these have been uploaded to the FTP center. Thanks! Rick

3. Rick Graziani graziani@cabrillo.edu3 Overview Students completing this module should be able to: Enable and disable CDP Use the show cdp neighbors command Determine which neighboring devices are connected to which local interfaces Gather network address information about neighboring devices using CDP Establish a Telnet connection Verify a Telnet connection Disconnect from a Telnet session Suspend a Telnet session Perform alternative connectivity tests Troubleshoot remote terminal connections

4. Rick Graziani graziani@cabrillo.edu4 Introduction to CDP Cisco Discovery Protocol (CDP) is a Layer 2 protocol that connects lower physical media and upper network layer protocols. CDP is used to obtain information about neighboring devices, such as: –the types of devices connected –the router interfaces they are connected to –the interfaces used to make the connections – the model numbers of the devices CDP is media and protocol independent, and runs on all Cisco equipment over the Subnetwork Access Protocol (SNAP).

5. Rick Graziani graziani@cabrillo.edu5 Information obtained with CDP CDP Version 2 (CDPv2) is the most recent release of the protocol. Cisco IOS (Release 12.0(3)T or later) supports CDPv2. CDP Version 1 (CDPv1) is enabled by default with Cisco IOS (Release 10.3 to 12.0(3)T).

6. Rick Graziani graziani@cabrillo.edu6 Implementation, monitoring, and maintenance of CDP Remote router’s interfaceThis router’s interface The cdp run command is used to enable CDP globally on the router. By default, CDP is globally enabled. The cdp enable command is used to enable CDP on a particular interface. On Cisco IOS Release 10.3 or higher, CDP is enabled by default on all supported interfaces to send and receive CDP information. CDP could be enabled on each of the devices interfaces by using the cdp enable command.

7. Rick Graziani graziani@cabrillo.edu7 Implementation, monitoring, and maintenance of CDP

8. Rick Graziani graziani@cabrillo.edu8 Implementation, monitoring, and maintenance of CDP

9. Rick Graziani graziani@cabrillo.edu9 Implementation, monitoring, and maintenance of CDP

10. Rick Graziani graziani@cabrillo.edu10 Implementation, monitoring, and maintenance of CDP

11. Rick Graziani graziani@cabrillo.edu11 Disabling CDP To disable CDP on a specific interface after it has been enabled, use the no CDP enable command in interface configuration mode.

12. Rick Graziani graziani@cabrillo.edu12 Troubleshooting CDP

13. Rick Graziani graziani@cabrillo.edu13 Getting Information about Remote Devices Establish a Telnet connection Verify a Telnet connection Disconnect from a Telnet session Suspend a Telnet session Perform alternative connectivity tests Troubleshoot remote terminal connections

14. Rick Graziani graziani@cabrillo.edu14 Telnet Telnet is a virtual terminal protocol that is part of the TCP/IP protocol suite. It allows connections to be made to remote hosts.

15. Rick Graziani graziani@cabrillo.edu15 Establishing and verifying a Telnet connection To initiate a Telnet session any of the following alternatives can be used: Denver>connect paris Denver>paris Denver>131.108.100.152 Denver>telnet paris A hostname table or access to DNS for Telnet must be present for a name to work. Otherwise, the IP address of the remote router must be entered.

16. Rick Graziani graziani@cabrillo.edu16 RouterA#conf t Enter configuration commands, one per line. End with CNTL/Z. RouterA(config)#ip host RouterA 10.1.1.1 RouterA(config)#exit RouterA#telnet routera Trying RouterA (10.1.1.1)... Open User Access Verification Password: RouterB> This is where the ip host commands can be helpful. Does not have to be the router-name but it is generally a good idea. Not case sensitive. Establishing and verifying a Telnet connection

17. Rick Graziani graziani@cabrillo.edu17 You must have the vty password set on the remote routers. We will always use cisco as our vty passwords! RouterA>telnet 10.1.1.1 Trying 10.1.1.1... Open Password required, but none set [Connection to 10.1.1.1 closed by foreign host] RouterA> RouterA>telnet 10.1.1.1 Trying 10.1.1.1... Open User Access Verification Password:cisco RouterB> RouterB>exit [Connection to 10.1.1.1 closed by foreign host] RouterA> RouterB(config)#line vty 0 4 RouterB(config-line)#login RouterB(config-line)#password cisco Configure vty password on RouterB Telnet works! Enter vty password Exit closes (ends) telnet session Telnet password – line vty

18. Rick Graziani graziani@cabrillo.edu18 RouterA>telnet 10.1.1.1 Trying 10.1.1.1... Open User Access Verification Password:cisco RouterB>ena % No password set RouterB>exit RouterA>telnet 10.1.1.1 Trying 10.1.1.1... Open User Access Verification Password:cisco RouterB>ena Password:class RouterB#exit [Connection to 10.1.1.1 closed by foreign host] RouterA> Cannot enter privilege mode because there is no privilege password (enable secret). Can only enter this mode from the console until the password is created. If there is no privilege password on the remote router, you cannot enter privilege mode! RouterB(config)#enable secret class Configure vty password on RouterB Telnet and the privilege password

19. Rick Graziani graziani@cabrillo.edu19 Disconnecting and suspending Telnet sessions A session is suspended for a limited time, to resume a Telnet session that has been suspended, just press Enter. The command show sessions will show what Telnet sessions are taking place.

20. Rick Graziani graziani@cabrillo.edu20 RouterA>connect Host: 10.1.1.1 Trying 10.1.1.1... Open User Access Verification Password:cisco RouterB> RouterA>show sessions Conn Host Address Byte Idle Conn Name * 1 10.1.1.1 10.1.1.1 0 0 10.1.1.1 RouterA> [Resuming connection 1 to 10.1.1.1... ] RouterB>exit [Connection to 10.1.1.1 closed by foreign host] RouterA>show sessions % No connections open RouterA> If there is no privilege password on the remote router, you cannot enter privilege mode! Or the “telnet” command Disconnecting and suspending Telnet sessions

21. Rick Graziani graziani@cabrillo.edu21 Advanced Telnet operation If the resume command is used it requires a connection ID. The connection ID is shown by using the show sessions command.

22. Rick Graziani graziani@cabrillo.edu22 Alternative connectivity tests As an aid to diagnosing basic network connectivity, many network protocols support an echo protocol. The ping target 172.16.1.5 in Figure responded successfully to all five datagrams sent. The exclamation points (!) indicate each successful echo. If one or more periods (.) are received instead of exclamations on the display, the application on the router (or source device) timed out waiting for a given packet echo from the ping target.

23. Rick Graziani graziani@cabrillo.edu23 Alternative connectivity tests More on ping (ICMP Echo) in a special presentation.

24. Rick Graziani graziani@cabrillo.edu24 Alternative connectivity tests The traceroute command is the ideal tool for finding where data is being sent in a network. If one of these routers is unreachable, three asterisks (*) will be returned instead of the name of the router. The traceroute command will continue attempting to reach the next step until the Ctrl-Shift-6 escape sequence is used.

25. Rick Graziani graziani@cabrillo.edu25 Troubleshooting IP addressing issues ping uses the ICMP protocol to verify the hardware connection and the IP address of the network layer. This is a basic testing mechanism. telnet verifies the application layer software between source and destination. This is the most complete test mechanism available. traceroute allows the location of failures in the path from the source to the destination. Trace uses Time to Live values to generate messages from each router along the path.

26. Rick Graziani graziani@cabrillo.edu26 Summary