1 pertemuan 8 getting information about remote devices

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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>



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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Password:ciscoRouterB>ena% No password setRouterB>exit



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


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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• More on ping (ICMP Echo) in a special presentation.

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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.

1 pertemuan 8 getting information about remote devices

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