Configure How the Client Authenticates to a Telnet Server

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Applies To: Windows 7, Windows 8, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Vista

You can use this procedure to configure how your Telnet client authenticates your user account with the Telnet server to which you are connecting.

Authentication is the means by which a user is identified and authorized. Telnet Server supports two methods of authentication: NTLM and plaintext. The authentication method attempted by the Telnet client must be set in Telnet command mode before attempting authentication with a remote system. For more information about the authentication modes available, see Configure Telnet Server Authentication.

In Telnet command mode, you can display the current NTLM authentication state, turn NTLM authentication on, or turn it off.

The authentication choices available to you are determined by the Telnet server to which you connect. If NTLM authentication is not available, then you must use plaintext authentication or you cannot successfully connect. This procedure enables you to configure your client to match the authentication modes offered by the server, and to select the best one if multiple modes are available.

Note

Changing the authentication mode while connected to a Telnet server has no impact on the current session. To see the effect of the change, you must disconnect and reconnect to the server.

Any user account can be used to complete this procedure.

Configuring authentication on a Telnet client

To view or configure your Telnet authentication settings, you can perform these procedures:

  • To display the current NTLM authentication state

  • To turn on NTLM authentication

  • To turn on password authenticaton

To display the current NTLM authentication state

  1. In the Telnet Client service, switch to command mode. See Switch Between Session Mode and Command Mode.

  2. At the Microsoft Telnet> command prompt, type d, and then press ENTER to display the current list of settings and their values.

  3. The output will include one of the following:

    • Will auth(NTLM Authentication). This indicates that NTLM authentication is enabled.

    • Won't auth(NTLM Authentication). This indicates that NTLM authentication is disabled, and that user IDs and passwords will be sent in plaintext. This is commonly referred to as password authentication.

To turn on NTLM authentication

  1. In the Telnet Client service, switch to command mode. See Switch Between Session Mode and Command Mode.

  2. At the Microsoft Telnet> command prompt, type set ntlm, and then press ENTER.

  3. Confirm that NTLM authentication is now enabled. See To display the current NTLM authentication state

To turn on password authentication

  1. In the Telnet Client service, switch to command mode. See Switch Between Session Mode and Command Mode.

  2. At the Microsoft Telnet> command prompt, type unset ntlm, and then press ENTER.

  3. Confirm that NTLM authentication is now disabled. See To display the current NTLM authentication state

Additional considerations

  • Although authentication data might be encrypted, the actual data being transferred can be read by anyone on the network. Because Telnet session traffic is not secure, ensure that no sensitive data is sent or received during a Telnet session.

  • If you connect to a computer running Telnet Server by using NTLM authentication, you cannot automatically access additional network resources because of a limitation of the NTLM authentication. In order to access other network resources during a Telnet session, you need to provide your user name and password again.

See Also

Concepts

Connect to a Telnet Server as a Standard User
Connect to a Telnet Server as an Administrator
Use IPv6 with Telnet Client