Upgrading the IOS version on your Cisco 3850 Catalyst switch is not something to be dreaded. In fact it should probably be rejoiced, as these days it most likely means you’re also catching up on patching some vulnerabilities on your device. While the upgrade process is a little different on the 3850 then older generations of the Catalyst switches, not much has changed. Overall it is an easy process that won’t take you long to complete.

What has changed is that the 3850 switch? Well the “operating system” that the hardware now runs on is called IOS-XE. Whereas previous generations of Cisco hardware ran on IOS software.

The IOS-XE software is delivered as a bundle containing a set of packages which your device will use. These packages, during the install step, will get expanded before they are actually installed on the device. The older generations of devices that ran IOS had a .bin file that was essenitally a “flat” image and not a bundle of packages. While there are other changes too, that is the main difference between the “new” IOS-XE and the “old” IOS.

Okay… Lets get our switch upgraded…

Step 1: Download the latest (or rather the recommended) IOS-XE version from the support portal of Cisco.com. (At the time of me writing this, the recommended release version is “Fuji-16.9.4”)

Step 2: Transfer the .bin file you downloaded in step 1 to your device. There are a few ways to so; TFTP or USB being the most common.

• Via TFTP

3850-SW# copy tftp flash:
Address or name or remote host []? 10.1.2.3
Source filename[]? cat3k_caa-universalk9.16.09.04.SPA.bin
Destination filename[cat3k_caa-universalk9.16.09.04.SPA.bin]?
Accessing tftp://10.1.2.3/cat3k_caa-universalk9.16.09.04.SPA.bin...
Loading cat3k_caa-universalk9.16.09.04.SPA.bin from 10.1.2.3: !!!!!!!!!!!!!

• Via USB

3850-SW# copy usbflash0:cat3k_caa-universalk9.16.09.04.SPA.bin flash:

Step 3: Start the Install.

3850-SW# software install file flash:cat3k_caa-universalk9.16.09.04.SPA.bin

Once the software install completes, you will need to reboot the switch so that it can boot into the freshly installed IOS-XE version.

3850-SW# reload

Step 4: Verify the new version. After rebooting the device in the previous step, you will want to verify that you are indeed running the new IOS version. You can run the following command to do so.

3850-SW# show version | i Switch
Cisco IOS Software [Fuji], Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version 16.9.4, RELEASE SOFTWARE (fc2)
Switch Ports Model SW Version SW Image Mode

Here we can see that the switch is running Fuji, and that it is on version 16.9.4. And now we’re done!