Cisco Nexus 1000V Security Configuration Guide, Release 4.2(1)SV2(2.1)
Configuring Telnet
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Configuring Telnet

This chapter contains the following sections:

Information About the Telnet Server

The Telnet protocol enables you to set up TCP/IP connections to a host. Telnet allows a user at one site to establish a TCP connection to a login server at another site and then pass the keystrokes from one device to the other. Telnet can accept either an IP address or a domain name as the remote device address.

Prerequisites for Telnet

You have configured IP on a Layer 3 interface, out of band on the mgmt 0 interface, or inband on an Ethernet interface.

Guidelines and Limitations for Telnet

  • The Telnet server is disabled by default
  • Cisco NX-OS commands may differ from Cisco IOS commands.

Default Setting for Telnet

Parameter

Default

Telnet server

Enabled

Configuring Telnet

Enabling the Telnet Server

The Telnet server is enabled by default, but you can reenable it if necessary.

Before You Begin

Log in to the CLI in EXEC mode.

Procedure
      Command or Action Purpose
    Step 1 switch# configure terminal 

    Enters global configuration mode.

     
    Step 2 switch(config)# feature telnet 

    Enables the Telnet server.

     
    Step 3 switch(config)# show telnet server 

    Enables the Telnet server.

     
    Step 4 switch(config)# show telnet server  (Optional)

    Displays the Telnet server configuration.

     
    Step 5 switch(config)# copy running-config startup-config  (Optional)

    Copies the running configuration to the startup configuration.

     

    This example shows how to enable the Telnet server:

    switch# configure terminal
    switch(config)# feature telnet
    switch(config)# show telnet server
    telnet service enabled
    switch(config)# copy running-config startup-config
    

    Starting an IP Telnet Session to a Remote Device

    Before You Begin
    • Log in to the CLI in EXEC mode.
    • Verify that the Telnet server is enabled and that it is also enabled on the remote device.
    • Obtain the hostname for the remote device and, if needed, the username on the remote device.
    Procedure
        Command or Action Purpose
      Step 1 switch# telnet {ip address | host-name} [port-number] [vrf vrf-name] 

      Creates an IP Telnet session to the specified destination.

      The keywords and arguments are as follows:

      • port-number—Port number, from 1 to 65535, to use for this session. The default port number is 23
      • vrf-name—Default VRF.
       

      Clearing Telnet Sessions

      Before You Begin

      Log in to the CLI in EXEC mode.

      Procedure
          Command or Action Purpose
        Step 1 switch# show users 

        Displays user session information.

         
        Step 2 switch# clear line vty-line 

        Clears a user Telnet session.

         
        Step 3 switch# show users  (Optional)

        Displays user session information.

         

        This example shows how to clear a Telnet session:

        switch# show users
        NAME     LINE         TIME         IDLE          PID COMMENT
        admin    tty1         Jul 25 19:13  old         2867
        admin    pts/1        Jul 28 14:04   .         31453 (::ffff:171.70.209.8)
        admin    pts/2        Jul 28 14:04   .         31475 (171.70.209.8)*
        switch# clear line 1
        switch# show users
        NAME     LINE         TIME         IDLE          PID COMMENT
        admin    tty1         Jul 25 19:13  old         2867
        admin    pts/2        Jul 28 14:04   .         31475 (171.70.209.8)*
        switch# 
        

        Verifying the Telnet Configuration

        Use the following commands to verify the configuration.

        Command

        Purpose

        show running-config security [all]

        Displays the user account configuration in the running configuration. The all keyword displays the default values for the user accounts.

        show telnet server

        Displays the telnet server configuration.

        show hosts

        Displays the configuration details for current hosts.

        show tcp connection

        Displays connection information.

        Feature History for Telnet

        This table only includes updates for those releases that have resulted in additions to the feature.

        Feature Name

        Feature Information

        Telnet

        4.0(4)SV1(1)

        This feature was introduced.