https://www.cisco.com/c/en/us/support/docs/smb/switches/
cisco-small-business-300-series-managed-switches/
smb4984-access-the-cli-via-putty-using-a-console-
connection-on-300-a.html

Step 1. Connect the switch to the computer using a
standard 9-pin serial cable.

The switch uses the factory default IP address of 192.168.1.254 by
default.

Enter the default login information:
• Username is cisco
• Default password is cisco (passwords are case sensitive

10 300 Series Managed Switches
115200 bits per second (with release 1.2.5 of the firmware,
autobaud detection is enabled by default
detect the speed after you press Enter
• 8 data bits
• no parity
• 1 stop bit
• no flow control
<legend>Reset at cli</legend>

https://www.cisco.com/c/en/us/support/docs/smb/switches/
cisco-small-business-300-series-managed-switches/
smb4985-administrator-password-recovery-for-300-
and-500-series-manag.html

Step 1. Access the CLI via a local console connection.

Step 2. Power cycle the switch by unplugging the power cord and
plugging it back in to the back of the device. After a couple of
seconds you should see the Cisco ASCII logo with a prompt to escape
the Autoboot loader. Press Return or Esc immediately to enter the
Startup Menu.

Note: Power cycle with the console cable and Putty connected. If the
device goes into Autoboot sequence, you can reattempt to enter the
Startup Menu by power cycling the device again.

Step 3. Select menu item 3. Password Recovery Procedure

Step 4. Press Enter to go back to the Startup Menu, and then press Esc
to exit. This will start the Autoboot sequence.

Step 5. After the switch has fully booted, you will be in password
recovery mode. However, before changing any usernames or passwords,
enter the following commands to avoid overwriting the existing
configuration on the switch:

    Switch#enable

    Switch#copy startup-config running-config

Note: In order to use backspace in the CLI, use the arrow keys to
highlight the desired character and then hit Backspace to delete the
character. You can also hold down Backspace to continuously delete
characters to the right of the highlighted cursor.

Step 6. In order to change the administrator password, you must enter
configuration mode. To enter configuration mode, enter one of the
following commands based on your access level:

    Switch(config)#username<new or previous username> privilege
    15 password <new password>

    Switch(config)#username admin privilege 15 password password

Note: Default password complexity settings require that the password
contain at least 3 character classes such as a capital letter, a
lowercase letter, and a number.

Step 8. Enter the following commands to exit configuration mode and
write to the configuration file.

    Switch#exit
    Switch#write

Step 9. Enter Y to overwrite the startup configuration file.

Step 10. Enter the following command to reboot the system so that
you can log in with your newly configured username and password:

    Switch#reload

Step 11. Enter Y to continue.  Your device will then reboot.