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103120 Views 7 Replies Latest reply: Feb 23, 2014 4:12 AM by Mark RSS

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line vty 0 4

Nov 7, 2013 4:12 AM

Steverino 375 posts since
May 3, 2010

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 5,351 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

  • 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.

  • Keith Barker - CCIE RS/Security, CISSP 5,351 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.

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

    thanks a lot

  • Neil John 455 posts since
    Jul 31, 2013
    Currently Being Moderated
    Re: line vty 0 4

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

  • Jon 74 posts since
    Aug 19, 2013
    Currently Being Moderated
    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.

  • 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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