Tài liệu học CCNA kỳ 2 mod4 CDP

1 Module 4 – Learning About Other Devices NIIT-ICT Hanoi info@niithanoi.vn 2 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 2 NIIT-ICT Hanoi info@niithanoi.vn 3 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). NIIT-ICT Hanoi info@niithanoi.vn 4 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). 3 NIIT-ICT Hanoi info@niithanoi.vn 5 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. NIIT-ICT Hanoi info@niithanoi.vn 6 Implementation, monitoring, and maintenance of CDP 4 NIIT-ICT Hanoi info@niithanoi.vn 7 Implementation, monitoring, and maintenance of CDP NIIT-ICT Hanoi info@niithanoi.vn 8 Disabling CDP To disable CDP on a specific interface after it has been enabled, use the no CDP enable command in interface configuration mode. 5 NIIT-ICT Hanoi info@niithanoi.vn 9 Troubleshooting CDP NIIT-ICT Hanoi info@niithanoi.vn 10 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 6 NIIT-ICT Hanoi info@niithanoi.vn 11 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. NIIT-ICT Hanoi info@niithanoi.vn 12 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. 7 NIIT-ICT Hanoi info@niithanoi.vn 13 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 NIIT-ICT Hanoi info@niithanoi.vn 14 • 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 8 NIIT-ICT Hanoi info@niithanoi.vn 15 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 priviledge password on RouterB Telnet and the privilege password NIIT-ICT Hanoi info@niithanoi.vn 16 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 takin g p lace. 9 NIIT-ICT Hanoi info@niithanoi.vn 17 RouterA>connect Host: 10.1.1.1 Trying 10.1.1.1 Open User Access Verification Password:cisco RouterB> RouterB> <control-shift-6, x> 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> <enter> [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 NIIT-ICT Hanoi info@niithanoi.vn 18 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. 10 NIIT-ICT Hanoi info@niithanoi.vn 19 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. NIIT-ICT Hanoi info@niithanoi.vn 20 Alternative connectivity tests • More on ping (ICMP Echo) in a special presentation. [...]... 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 NIIT-ICT Hanoi info@niithanoi.vn 22 11 Summary NIIT-ICT Hanoi info@niithanoi.vn 23 12 ... 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 NIIT-ICT Hanoi info@niithanoi.vn 21 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