Guide to Change the Password on a 3750 Switch

1. How to Change the Password on a 3750 Switch?
The Cisco 3750 switch has contributed greatly to Cisco's success in the
networking hardware market. Its features provide efficient and reliable
network switching services. You can find a pre-owned 3750 model at a
good price, and if you do buy a pre-owned Cisco 3750 switch, you may
need to change the password before you are able configure it to work on
your network. Fortunately, Cisco has provided a built-in procedure that
allows you to change the password.
Things You'll Need
Cisco 3750 switch and serial cable
Computer with terminal emulation software

2. How to Change the Password on a Catalyst 3750 Switch？
1. Connect your computer to the 3750 switch using the blue serial cable
that typically comes with it. Connect the 9-pin d-shell connector to your
computer's serial port, and connect the RJ-45 connector to the switch's
console port.
2. Configure a terminal session to the switch. Power up your computer,
open a terminal emulator application, and configure a terminal session
with the following settings:
9600 baud
no parity
1 stop bit
8 data bits
Xon/Xoff flow control

3. Save the configuration with a name that you can recognize later.
3. Hold down the "Mode" button on the left front of the Cisco 3750
switch, and plug in the power cable. Five seconds after the Stat LED goes
off, release the "Mode" button. The SYST LED should start to blink amber.
4. At the command prompt, issue the following commands to the switch
to prepare it for the reset procedure, and rename the current
configuration file:
flash_init
load_helper
dir flash:
renameflash:config.textflash:config.old
5. Boot the 3750 switch by issuing the "boot" command and pressing
"Enter." At the "System Configuration Dialog" prompt, answer "n" and
press "Enter" twice. This should display the "Switch>" prompt.
6. Issue the "en" command at the prompt, and press "Enter." You should
see the prompt change from "Switch>" to "Switch#." Rename the
configuration file with the following command:

4. renameflash:config.oldflash:config.text (press "Enter")
Press "Enter" to accept the destination filename default.
7. Copy the configuration file into the 3750 memory with the following
command:
copyflash:config.textsystem:running-config
Press "Enter" when prompted for a destination filename to accept the
default.
8. eate new passwords for the 3750 switch with the following
commands:
conf t
enable secret spswd (spswd = your new secret password)
enable password enpswd (enpswd = your new enable password)
linevty 0 15
passwordtpswd (tpswd = your new terminal password)
login
line con 0

5. passwordcpswd (cpswd = your new console password)
write memory
The Cisco 3750 will issue a "Building Configuration" message. When you
see the [OK] message at the Sw1# prompt, you have completed the
password change for the Cisco 3750 switch.
References:
Cisco Catalyst Fixed Configuration Layer 2 and Layer 3 Switches