How to Upgrade IOS on Cisco 3850

Upgrading the IOS on a Cisco 3850 switch is a crucial task to ensure your network device is running the latest features and security updates. Follow these steps to perform the upgrade:

Prerequisites

Backup Configuration: Ensure you have a backup of the current configuration.
Download the IOS Image: Obtain the latest IOS image from the Cisco website.
TFTP Server: Set up a TFTP server to transfer the IOS image to the switch.

Steps to Upgrade

Verify Current IOS Version:
- Connect to the switch via console or SSH.
- Run the command: show version
- Note the current IOS version and the switch model.
Transfer the IOS Image to the Switch:
- Copy the IOS image to the TFTP server.
- Use the following command to transfer the image to the switch:
```
copy tftp: flash:
```
- Follow the prompts to enter the TFTP server IP address and the IOS image filename.
Verify the IOS Image:
- Ensure the image is correctly copied by verifying its checksum:
```
verify /md5 flash:
```
Set the Boot Variable:
- Configure the switch to boot from the new IOS image:
```
config terminal
boot system flash:
end
```
- Save the configuration:
```
write memory
```
Reload the Switch:
- Reboot the switch to load the new IOS image:
```
reload
```
- Confirm the reload when prompted.
Verify the Upgrade:
- After the switch reboots, verify the new IOS version:
```
show version
```
- Ensure the switch is running the new IOS image and all configurations are intact.

Post-Upgrade Steps

Test Connectivity: Ensure all network connections are functioning correctly.
Monitor the Switch: Keep an eye on the switch for any unusual behavior or logs.

By following these steps, you can successfully upgrade the IOS on your Cisco 3850 switch, ensuring it operates with the latest features and security enhancements.