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"% Authentication failed" message occurs when trying to log into router

This error message occurs when AAA authentication is configured globally (default) on the router but no AAA server is setup to process the request and no alternative authentication method is specified for line console 0.

Rack-1#r4

Trying R4 (1.1.1.1, 2036)... Open

% Authentication failed

R4 con0 is now available

Press RETURN to get started.

  • If the running-config has not been saved yet, a simple power cycle of the router or switch will fix the error and you would be able to reconnect. You can power cycle the router via Remote Power Controller (see Using The Remote Power Controller guide).
  • If the running-config has already been saved to the start-up config, then the start-up config needs to be bypassed in order to remove the aaa authentication commands. The router will need to be booted up in rommon mode to change the config register. Below are the steps to complete this process:

Bypass the startup-config For Routers R1 - R6

1.  Power cycle the router using the Remote Power Controller (see Using The Remote Power Controller guide).

2.  As the router starts booting up, interrupt the boot sequence by pressing the break sequence a few times. The break sequence will send the router into rommon mode. See below for common break sequence keys:

  • For Putty and SecureCRT, press Ctrl+Break to enter rommon mode.
  • For TeraTerm press Alt+b keys.
  • For the break sequence of other telnet clients, refer to the list of Standard Break Key Sequence Combinations.

3.  Once the router is in rommon mode, change the config register to 0x2142. This will force the router to bypass the startup config saved in NVRAM. This does not delete the startup-config but simply tells the router not to load it during the startup process.

        rommon 1 > confreg 0x2142

You must reset or power cycle for new config to take effect
rommon 2 > reset

4.  The router will reload and will prompt to enter the configuration dialogue. Type "no" at the prompt.

--- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [yes/no]: no

Press RETURN to get started!

5. Change the config register back to 0x2102 to avoid your config from being bypassed again should you need to reload the device during your lab and for the next person who uses the rack.

Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#config-register 0x2102
Router(config)#

Note: If you save the running-config at this point, you will overwrite any changes you made to the startup-config with the current running-config.

Bypass the startup-config For Switches SW1 - SW4

1.  Power cycle the switch using the Remote Power Controller (see Using The Remote Power Controller guide).

2.  As the switch starts booting up, interrupt the boot sequence by pressing the break sequence a few times. This break sequence will send the switch to rommon mode. See below for common break sequence keys:

  • For Putty and SecureCRT, press Ctrl+Break to enter rommon mode.
  • For TeraTerm press Alt+b keys.
  • For the break sequence of other telnet clients, refer to the list of Standard Break Key Sequence Combinations.

3.  Once the switch is in rommon mode, initialize the flash with the flash_init command. On some switches, the load_helper command is also necessary. After that delete the flash:config.text file and boot the switch. Alternatively you can rename the flash:config.text file instead of deleting it. Here are the series of commands to enter:

switch: flash_init
Initializing Flash...
flashfs[0]: 168 files, 3 directories
flashfs[0]: 0 orphaned files, 0 orphaned directories
flashfs[0]: Total bytes: 32514048
flashfs[0]: Bytes used: 29597696
flashfs[0]: Bytes available: 2916352
flashfs[0]: flashfs fsck took 14 seconds.
...done Initializing Flash.
Setting console baud rate to 9600...

switch: load_helper

switch: delete flash:config.text
Are you sure you want to delete "flash:config.text" (y/n)?y
File "flash:config.text" deleted

switch: boot

Loading "flash:/c3560-advipservicesk9-mz.122-46.SE.bin"...@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
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