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169240 Views 16 Replies Latest reply: Jan 8, 2015 2:08 AM by Isaac RSS 1 2 Previous Next

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line vty 0 4

Jan 20, 2015 11:35 AM

Steverino 375 posts since
May 3, 2010
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My understanding is that this enter configuration mode for the vty lines, but what are the vty lines?  are they used for telnet connections to the device youre configuring?

  • Keith Barker - CCIE RS/Security, CISSP 5,327 posts since
    Jul 3, 2009
    Currently Being Moderated
    1. May 15, 2010 4:22 PM (in response to Steverino)
    Re: line vty 0 4

    skiefling37 wrote:

     

    My understanding is that this enter configuration mode for the vty lines, but what are the vty lines?  are they used for telnet connections to the device youre configuring?

     

     

    Yes, they are logical "connection points" to the router, that are used by Telnet as well as SSH to remotely access your router.

     

    Some routers and switches, can support more than just the 5 ( 0-4 ).

     

    Take a look at the diagram:

     

    3 routers in line.jpg


    With the following configuration on R3, when a user connects via telnet, they will be prompted for a username, and the username will be checked on R3 from the configuration.


    R3(config)#line vty 0 4
    R3(config-line)#login local
    R3(config-line)#exit
    R3(config)#username Steve password cisco

     


     

    When I telnet from the remote network address of 10.0.0.1, to R3, and issue the command "who"  it will show me who is connected.


    R1#telnet 3.3.3.3
    Trying 3.3.3.3 ... Open


    User Access Verification

     

    Username: steve
    Password: <cisco>  the password does not show on the screen
    R3>


    R3>who
        Line       User       Host(s)              Idle       Location
       0 con 0                idle                 00:02:53
    * 98 vty 0     steve      idle                 00:00:00 10.0.0.1

     

     

     

    The output above reflects that a user is connected (steve) coming in from 10.0.0.1, and is currently connected through the logical interface of "vty 0".   If another user connected, they would be connected on vty 1 and so forth.  If all vty lines were in use, the 6th user would not be allowed access.

     

    The output also shows that someone is connected to the serial console port as well.

     

     

     

     

    Best wishes,

     

     

    Keith

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  • smraza 16 posts since
    Jan 25, 2010
    Currently Being Moderated
    Re: line vty 0 4

    it means at a time 5 user can access R3 through telnet ? am i right ? please confirm.

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  • Keith Barker - CCIE RS/Security, CISSP 5,327 posts since
    Jul 3, 2009
    Currently Being Moderated
    3. May 15, 2010 7:48 PM (in response to smraza)
    Re: line vty 0 4

    smrazaccna10 wrote:

     

    it means at a time 5 user can access R3 through telnet ? am i right ? please confirm.

    Yes.  If a device has lines VTY 0 - 4, 5 users can access through telnet at the same time.

     

    Keith.

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  • smraza 16 posts since
    Jan 25, 2010
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    Re: line vty 0 4

    thanks a lot

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  • Neil John 456 posts since
    Jul 31, 2013
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    Re: line vty 0 4

    I got it hahaha thanks alot this is very informative about vty lines :))

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  • Jon 77 posts since
    Aug 19, 2013
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    6. Oct 8, 2013 1:18 PM (in response to Neil John)
    Re: line vty 0 4

    I have seen routers with a lot of VTYs, just to a #line vty ? and you will see the number of cocurrent lines that are supported.

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  • Mark 23 posts since
    Dec 13, 2013
    Currently Being Moderated
    7. Feb 23, 2014 4:12 AM (in response to Steverino)
    Re: line vty 0 4

    As best practice I would recommend that you always prompt for a password when configuring telnet or any remote access. So:

     

    line vty 0 4

    login

    password <some secure password>

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  • Clyde Veigas 3 posts since
    Feb 13, 2014
    Currently Being Moderated
    Re: line vty 0 4

    I'm a little confused, so if 5 users telnet at the same time, all of them have to login with username "steve" and password "cisco" ??

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  • Conwyn 9,657 posts since
    Sep 10, 2008
    Currently Being Moderated
    9. Aug 5, 2014 11:08 AM (in response to Clyde Veigas)
    Re: line vty 0 4

    Hi Clyde

     

    They do not need a username but if you choose login local you can define hundreds to choose from.

     

    Regards Conwyn

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  • Clyde Veigas 3 posts since
    Feb 13, 2014
    Currently Being Moderated
    10. Aug 6, 2014 1:57 AM (in response to Conwyn)
    Re: line vty 0 4

    Hey Conwyn,

     

    So you are saying that if there were 3 users named A, B and Steve... even A and B has to use username "steve" and password "cisco" to gain access ?? , assuming if only the following commands were configured...

     

    R3(config)#line vty 0 4

    R3(config-line)#login local

    R3(config-line)#exit

    R3(config)#username Steve password cisco

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  • Currently Being Moderated
    11. Aug 6, 2014 8:40 PM (in response to Steverino)
    Re: line vty 0 4

    Hi Steverino and all,

    You can also check this article

    http://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-software-releases-110/45843-configpasswords.html

    Under "Background Information", there are some definitions related to lines (CTY, TTY, AUX and VTY). Hope that helps!

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  • Currently Being Moderated
    12. Aug 6, 2014 10:16 PM (in response to Fabiola)
    Re: line vty 0 4

    Dear Clyde,

    As there is no restrictions regarding different VTY lines to be used different types of password protection. In fact, you can configure routers with a single password for the it and user-specific passwords for other inbound connections.

     

    clear line vty - can be used to free up the in-use vty lines.

    show sessions - can be used for checking the active sessions.

     

    Hope it helps !!

     

    -

    Parvesh

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  • Krushna 1 posts since
    Oct 1, 2014
    Currently Being Moderated
    13. Nov 17, 2014 6:20 AM (in response to Parvesh)
    Re: line vty 0 4

    hello everybody,

     

    as i m learning basic concepts of ccna...can anyone plz tell me what is exactly long form or meaning of " VTY" ??

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  • Richard 6 posts since
    Jun 18, 2014
    Currently Being Moderated
    14. Nov 17, 2014 6:36 AM (in response to Krushna)
    Re: line vty 0 4

    https://learningnetwork.cisco.com/message/445138#68207

    Hi,

    Keith Barker's answer at the very top of this thread provides a very thorough explanation with diagrams and associated explanation. I have provided the link at the begin of this reply

    Thanks

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