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DESCRIPTION
3 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.
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Pertemuan 8 Getting Information about Remote
Devices
Discussion Topics
• Telnet• Establishing and verifying a Telnet connection• Disconnecting and suspending Telnet sessions• Advanced Telnet operation• Alternate connectivity tests• Troubleshooting IP address issues
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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.
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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.
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RouterA#conf tEnter configuration commands, one per line. End with CNTL/Z.RouterA(config)#ip host RouterA 10.1.1.1RouterA(config)#exit
RouterA#telnet routeraTrying 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
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RouterA>telnet 10.1.1.1Trying 10.1.1.1 ... Open
Password required, but none set
[Connection to 10.1.1.1 closed by foreign host]RouterA>
RouterA>telnet 10.1.1.1Trying 10.1.1.1 ... Open
User Access Verification
Password:ciscoRouterB>RouterB>exit
[Connection to 10.1.1.1 closed by foreign host]RouterA>
RouterB(config)#line vty 0 4RouterB(config-line)#loginRouterB(config-line)#password cisco
Configure vty password on RouterB
Telnet works! Enter vty password
Exit closes (ends) telnet session
Telnet password – line vty
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RouterA>telnet 10.1.1.1Trying 10.1.1.1 ... Open
User Access Verification
Password:ciscoRouterB>ena% No password setRouterB>exit
RouterA>telnet 10.1.1.1Trying 10.1.1.1 ... Open
User Access Verification
Password:ciscoRouterB>enaPassword:classRouterB#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.
RouterB(config)#enable secret classConfigure vty password
on RouterB
Telnet and the privilege password
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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.
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RouterA>connectHost: 10.1.1.1Trying 10.1.1.1 ... Open
User Access Verification
Password:ciscoRouterB>RouterB> <control-shift-6, x>
RouterA>show sessionsConn 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 openRouterA>
Or the “telnet” command
Disconnecting and suspending Telnet sessions
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Advanced Telnet operation
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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.
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Alternative connectivity tests
• More on ping (ICMP Echo) in a special presentation.
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Alternative connectivity tests
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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.
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