Pertemuan 8
Getting Information about Remote
Devices
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Discussion Topics
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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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Establishing and verifying a
Telnet connection
RouterA#conf t
Enter configuration commands, one per line. End with CNTL/Z.
RouterA(config)#ip host RouterA 10.1.1.1
Does not have to be
RouterA(config)#exit
the router-name
but it is generally a good idea.
RouterA#telnet routera
Trying RouterA (10.1.1.1)... Open
Not case sensitive.
User Access Verification
Password:
RouterB>
• This is where the ip host commands can be helpful.
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Telnet password – line vty
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>
RouterB(config)#line vty 0 4
Configure vty password
RouterB(config-line)#login
RouterB(config-line)#password cisco
on RouterB
RouterA>telnet 10.1.1.1
Trying 10.1.1.1 ... Open
User Access Verification
Password:cisco
RouterB>
RouterB>exit
Telnet works! Enter vty password
Exit closes (ends) telnet session
[Connection to 10.1.1.1 closed by foreign host]
RouterA>
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Telnet and the privilege
password
RouterA>telnet 10.1.1.1
Trying 10.1.1.1 ... Open
User Access Verification
Password:cisco
RouterB>ena
% No password set
RouterB>exit
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.
Configure vty password
on RouterB
RouterB(config)#enable secret class
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>
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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
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taking place.
Disconnecting and suspending Telnet
sessions
RouterA>connect
Or the
Host: 10.1.1.1
Trying 10.1.1.1 ... Open
“telnet” command
User Access Verification
Password:cisco
RouterB>
RouterB> <control-shift-6, x>
RouterA>show sessions
Conn Host
* 1 10.1.1.1
Address
10.1.1.1
Byte
0
Idle Conn Name
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>
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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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