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"%MGMT-5-LOGIN_FAIL:User failed to log in from Console" messages appear when Telnetted into a switch with a modem attached to the console port due to misconfiguration on the modem


Core issue

Modem misconfiguration may cause %MGMT-5-LOGIN_FAIL:User failed to log in from Console messages to appear when Telnetting into the switch. User may also see a long string of garbage characters appear on the screen.


%MGMT-5-LOGIN_FAIL:User failed to log in from Consolemessages may appear when a modem is attached to the console port of a switch. This may be due to a configuration issue on the modem which causes the switch  to detect that the modem is repeatedly requesting authentication.

This message can possibly be a problem with the terminal server connected to the console port of the switch. When the switch console is connected to an async line of a terminal server and a soft reset is performed on the switch, a stream of garbage (random characters) will stream across the screen for several minutes. If Terminal Access Controller Access Control System (TACACS) is enabled on the switch, several minutes can turn into several days as the garbage is buffered piece-by-piece and processed by TACACS. The workaround is to configure no exec on the async line that the switch is connected to. Please note that even after configuring no exec, the messages will continue until the buffer is clear.

If the modem attached is a 3COM/US Robotics model, try the following settings:

  1. Set dip switches to 3,8 down, all others up.
  2. Connect modem to PC.
  3. Run hyperterminal and connect to modem at 9600 baud.
  4. Send init string: at&fs0=1&c1&h0&d2&r2&b1&m4&k0&n6&w.
  5. Set dip switches to 1,4,8 down, all others up.
  6. Connect modem to console port with appropriate cable.

Or, try the following init strings:



For more information on connecting modems to Catalyst switches, refer to Connecting a Modem to the Console Port on Catalyst Switches. Also, refer to the Related Information section at the bottom of that document.