Resetting Cisco 3800 Series Routers

Introduction

Cisco's 3800 series include 4 different type of routers: Cisco 3825, Cisco 3825-NOVPN, the Cisco 3845, and the Cisco 3845-NOVPN. Depending on the series of the router, there will be different methods of resetting. All Cisco routers will use the ROMMON mode to reset if a password was configured. ROMMON mode is to be used for troubleshooting purposes, or if a password from a previous configuration has been forgotten. The following is the method to reset a Cisco 3800 Series router.

Clearing Configurations on a Cisco 3800

If a router has a previous configuration, a network administrator may have to clear the configurations in order to configure the necessary components needed on a network. As such, ensure that the router is accessible; SSH or Telnet can be used to remote access, but otherwise access through console. Before proceeding to clear the configurations, connect the console rollover cable. The pin-end should be connected to the corresponding port on the host device, and the RJ45 end should be connected to the console port found behind the router. A terminal to get access the router is needed. Some popular terminals include TeraTerm, PuTTY, and SecureCRT (make sure to have any of these installed on the host device) .

Key Items Needed

• Host Computer
• Rollover Console Cable
• Terminal Emulator (I.e. TeraTerm, SecureCRT, PuTTY)

Clearing Configurations

Be sure to always clear all configurations of the 3800 if it is not being used.

Step One: Hardware

Plug in the power cable of the router to an open outlet. Connect to the router using a console cable (usually light blue).

• NOTE: The RJ45 end of the console cable connects to the corresponding console port on the router, and the pin end connects to the corresponding port on the host device.

Turn on the host computer and the Cisco 3800 router by flipping the switch. Make sure that all lights on the router are on and identified as a light green.

Step Two: Terminal Programs

From the host computer, open any of the terminal emulators installed. A window will open with a menu of settings prior to accessing the router. By default, the menu should already be set, assuming console connection.

• NOTE: If the router is being consoled, then ensure that the terminal is set to Serial Com 1.

Once the menu is set, click OK. The router will boot and open its configuration files.

Step Three: Booting

Upon booting, the router may input the following message:

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

Respond to the message by typing no, and then hit enter. Depending on the age of the router and the amount of configurations, the router may take awhile to process the no message. After it loads, the following message will show:

• Press RETURN to get started

From here, you would press enter. Then you will enter the hidden page.

Step Four: Clearing Process

After hitting enter, you will be in User Exec Mode once the following output shows:

• [Hostname]>

All the show commands are available in Privileged Exec Mode. To enter this mode, type enable:

• [Hostname]>enable

A signaler that indicates that you have entered Privileged Exec is by the pound symbol at the end of the command line:

• [Hostname]#

The first thing you should do is ensure that there is a saved configuration file. You would have to use a series of show commands to verify. Some of the show commands you can use are as follows:

• [Hostname]#show ip int brief - This command specifically shows which interfaces on the router have been assigned IP addresses. It can be used as an indicator that there is indeed a saved configuration file.
• [Hostname]#show running-config - This command will show ALL the configurations including any configured protocols, encapsulation methods, and etc.

Once you have verified that there is a saved file, enter the following command to delete the configuration file:

• [Hostname]#erase startup-config
  • NOTE: The router will ask you if you are sure about deleting the file. Simply press enter.

Step Five: Reload/Verification

NOTE: It is crucial that you reload the router once you delete the file. The following command will essentially reboot the router to a "factory" state:

• [Hostname]#reload
  • NOTE: The computer will begin to reboot. It might look like it is frozen, but it really isn't. The router is is processing the blank file and is trying to assume its factory state. DO NOT EXIT THE TERMINAL, AND DO NOT SPAM ANY KEYS. BY DOING SO, THE ROUTER WILL ASSUME THAT IT IS TO ABORT THE REBOOT, AND YOU WOULD HAVE TO DO THE PROCESS ALL OVER AGAIN

A signaler that the reboot is working is if you see the router spamming symbols such as #####, or &&&&&. The router will then show the prompts under Step Three. You would follow the same steps. To verify that the 3800 is blank, use the show commands under Step 4.

Common Issues & Troubleshooting

Often, with a pre-configured router, there will be a password that a network technician or administrator might not be able to identify. These passwords are crucial for accessing the router itself and deleting the configuration file. If the password is not known, a mode called ROMMON would have to be used in order to delete that password from the configuration file, and allow access into the router.

ROMMON Method

Booting into ROMMON is a bit different than booting into the router's default mode:

Step 1

Follow the same Hardware and Software steps on the Clearing Configurations section.

Step 2

Perform a break by holding down ALT + B upon boot.

• NOTE: Do NOT let go of these keys. Hold them down until you see the following prompt: Rommon 1>
• SECOND NOTE: the number after the ROMMON prompt does not affect commands.

Step 3

• Type the command: confreg 0x2142 and hit enter. What this command does, is that it will command the router to boot from Flash. It will essentially bypass the startup configuration where the passwords are stored.
  • Rommon 1>confreg 0x2142

Step 4

Now type the reset command on the next prompt. This will allow the router to reboot and ignores any of the saved configurations:

• Rommon 1>reset

Step 5

The router will now reboot and may take a few minutes. Make sure NOT to press any keys that can possibly abort the reboot.

• For any setup questions, type No.

Step 6

Once the router finishes booting, hit enter when the following prompt shows:

• Press RETURN to get started

Step 7

Hit enter to go into User EXEC Mode.

Step 8

Enter Privileged EXEC Mode by typing enable.

Step 9

Now all you have to do is verify that the saved file is deleted using show commands:

• [Router Name]#show running-config
  • NOTE: If necessary, or just to be sure, you may use the erase startup-config command:
    • [Router Name]#erase startup-config

Quick Notes

All the documentation above is specifically for Cisco 3800 Series routers. As far as the hardware and software aspect, everything will be pretty much the same regardless of the Cisco device. The only method that differs between Cisco devices, are booting into ROMMON and the confreg command to boot into Flash.