Login Failure Through Telnet

Procedure

1. Check whether the number of login users reaches the upper limit.

   Log in to the switch through the console port and run the display users command to check whether all VTY user interfaces are in use. By default, a maximum of five users are allowed by a VTY channel. You can run the display user-interface maximum-vty command to check the maximum number of users allowed by the current VTY channel.

   If the number of login users reaches the upper limit, run the user-interface maximum-vty 15 command to increase the maximum number of login users to 15. Then configure the supported protocol type, authentication mode, and user privilege level on the extended VTY user interface.

2. Check whether an ACL is configured in the VTY user interface view. (Telnet IPv4 is used as an example)

   Run the user-interface vty command on the Telnet server to enter the user interface view and then run the display this command to check whether an ACL is configured in the VTY user interface view. If so, record the ACL number.

   Run the display acl acl-number command on the Telnet server to check whether the IP address of the Telnet client is denied in the ACL. If so, run the undo rule rule-id command in the ACL view to delete the deny rule and then run the corresponding command to modify the ACL and permit the IP address of the client.

3. Check whether the access protocol is correctly configured in the VTY user interface view.

   Run the user-interface vty command on the Telnet server to enter the user interface view and then run the display this command to check whether protocol inbound is set to telnet or all. By default, the system supports the SSH protocol. If not, run the protocol inbound { telnet | all } command to allow Telnet users to log in to the switch.

4. Check whether an authentication mode is set for login users in the user interface view.

   Run the display this command in the VTY user interface view to check the login authentication mode.

   • If password authentication is configured using the authentication-mode password command, you must enter the password upon login.

   • If AAA authentication is configured using the authentication-mode aaa command, you must run the local-user command to create a local AAA user.