The Cisco 3925 router is part of a family of networking equipment produced by Cisco, which has been a network equipment giant for many years. Used 3925 routers are available on the Internet at reasonable prices, so acquiring one is not difficult. However, if the password is unknown or lost, reconfiguration is impossible until the password is reset or recovered. Cisco has built in a procedure for rescuing lost or forgotten passwords or entering new passwords.
Connect your computer to the router with the blue serial-to-RJ-45 cable that came with the router. The 9-pin D-shell end connects to your computer's serial port, while the RJ-45 end connects to the console jack on the router. The RJ-45 end resembles a slightly larger telephone jack connector.
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Turn on your computer and establish a terminal session to the 3925. You can use any terminal emulator, and many are freely available on the Internet. Configure the session settings as follows:
9600 baud 8 data bits No parity 1 stop bit No flow control
Plug the router's power cable into an electrical outlet, and as the 3925 boots, you should see the Cisco boot messages. If you don't see any output on your computer's terminal session, check your settings on the session and restart it if necessary. Press "Break" within 30 seconds of powering on the router to enter rommon (ROM monitor) mode.
Type "confreg 0x2142" and press "Enter" at the "rommon 1>" prompt. This will cause the router to boot from its internal flash memory without loading the configuration into memory. At the following "rommon 2>" prompt, type "reset" and press "Enter." This will cause the router to reload and ignore the previously saved configuration file.
Respond "no" and press "Enter" when prompted for responses to enter the initial dialog or basic management setup. Type "enable" and press "Enter" at the following "Router>" prompt. This will put you into enable mode and display the "Router#" prompt. Copy the non-volatile memory into memory with the "copy startup-config running-config" command, followed by the "Enter" key. Type "sho run" at the prompt and press "Enter" to display the current configuration, including the passwords, some of which may be encrypted.
Type "config t" at the prompt and press "Enter." At the "Router(config)#" prompt, type "enable secret
Type "config t" at the "Router#" prompt and press "Enter." At the "Router(config)#" prompt, type "config-register 0x02102" and press "Enter" to reset the boot register to its normal setting. Press "Ctrl" + "z" to leave configuration mode. Type "copy running-config startup-config" and press "Enter" to save your changes. Reboot the router and you should be able to login with your password.
Things You'll Need
Serial to RJ-45 cable
Terminal emulation software