how to update a cisco sw to the new ios

Updating the IOS (Internetwork Operating System) on a Cisco switch involves a set of steps to ensure the switch is upgraded safely and correctly. Here’s a general guide on how to update the IOS on a Cisco switch:

### Pre-requisites:
1. **Check Compatibility:** Ensure that the new IOS version is compatible with your switch model.
2. **Download IOS Image:** Obtain the correct IOS image file from Cisco's website or your organization's repository. You will need a valid Cisco Smart Account to download IOS images.
3. **Backup Configuration and Current IOS:** Before proceeding, backup your current configuration and IOS image.
4. **TFTP/FTP Server:** Have access to a TFTP or FTP server to host the new IOS image.

### Steps to Update IOS on a Cisco Switch:

1. **Connect to the Switch:**
   - Use a console cable to connect your PC to the switch's console port, or SSH into the switch if it's accessible over the network.

2. **Verify Current IOS Version:**
   ```bash
   show version
   ```

3. **Backup Current Configuration:**
   ```bash
   copy running-config startup-config
   ```

4. **Backup Current IOS Image (optional):**
   You may want to back up the current IOS image if you don't already have it saved.
   ```bash
   copy flash: backup-ios.bin
   ```

5. **Transfer the New IOS Image:**
   Use a TFTP/FTP server to transfer the new IOS image to the switch. The command will look like this when using TFTP:
   ```bash
   copy tftp: flash:
   ```
   Follow the prompts to provide the TFTP server's IP address and the IOS image filename.

6. **Verify the IOS Image:**
   After the file transfer is complete, verify the integrity of the new IOS image:
   ```bash
   verify flash:new-ios-image.bin
   ```

7. **Set the Boot Variable:**
   Set the switch to boot from the new IOS image at startup.
   ```bash
   boot system flash:new-ios-image.bin
   ```

8. **Save the Configuration:**
   Save the boot configuration:
   ```bash
   write memory
   ```

9. **Reload the Switch:**
   Restart the switch to load the new IOS image:
   ```bash
   reload
   ```

10. **Verify the Upgrade:**
    After the switch reboots, verify that the new IOS version is running.
    ```bash
    show version
    ```

### Important Notes:
- Ensure that all configurations are saved before reloading.
- If you encounter issues during the update, you can revert back to the old IOS image if you have it saved.
- If possible, test the upgrade in a lab environment before applying it to production devices.

### Additional Tips:
- It’s advisable to schedule downtime for the switch upgrades to avoid disruption in service.
- Consult the release notes of the new IOS for any changes in commands or new features that may impact your network configuration.

By following these steps, you should be able to update the IOS on your Cisco switch successfully.