How to Upgrade IOS on Cisco Routers

Cisco routers have a reputation for good performance, reliability and a long list of features. However, cisco router software still require updates for security, defects and feature enhancements. Changing the Cisco router operating system image (the IOS) is a straightforward procedure that can be performed in about 30 minutes.

Things You'll Need
Microsoft Windows 7 computer with telnet client and TFTP service installed
IP address of the Microsoft Windows 7 computer
Cisco router with telnet service enabled
IP address of the Cisco router
Cisco IOS image located in the TFTP service root directory
Password for the Cisco router telnet connection
Privilege Exec mode password for the Cisco router

Steps to upgrade IOS on cisco 871 router
1. Click the "Globe" button, then select the "Search" box, and then type "cmd." Right-click on the command line icon that appears and click "Run as Administrator." The command line window will appear.

2. Enter "telnet x.x.x.x," on the command prompt, replacing the "x.x.x.x" with the IP address of a Cisco router, and then press the "Enter" key. Telnet will then connect to the Cisco router.

3. Enter the telnet password when requested on the command prompt, and then tap the "Enter" key.

4. Enter "enable" on the command prompt, and tap the "Enter" key. Type the Privilege Exec password for the Cisco router when requested, and press the "Enter" key.

5. Enter the "copy tftp flash" command on the command prompt, and then tap the "Enter" key.

6. Enter the IP address of the Windows 7 computer on the command line as the IP address of the TFTP server from which to copy the new IOS image, and then tap the "Enter" key.

7. Enter the exact name of the IOS file on the command prompt when requested, and then tap the "Enter" key.

8. Enter the name of the IOS file as the destination file name and tap the "Enter" key.

9. Type "Y" when the "Erase flash: before copying? [confirm]" message appears, and press the "Enter" key. The new IOS file will then be copied to the cisco 877 router flash drive.

10. Enter "configure terminal" on the command line, and then tap the "Enter" key.

11. Type "no boot system" and press the "Enter" key. Then type "boot system flash:ios_filename," except replace the "ios_filename" with the exact name of the IOS file that was just transferred to the Cisco router, and then tap the "Enter" key.

12. Type the "exit" command at the command prompt and tap the "Enter" key, and then type "write memory" and tap the "Enter" key.

13. Enter the "reload" command on the command prompt, and then press the "Enter" key. The Cisco router will restart and boot into the new cisco router IOS.