There is somewhat of a major caveat when upgrading to IOS XE Gibraltar 16.11.1 that you must consider before upgrading.

When upgrading to IOS XE 16.11.1, on Cisco Catalyst 9500 Series Switches (C9500-24Y4C, C9500-32C, C9500-32QC, and C9500-48Y4C) . The default switchport state changes from a Layer 3 switchport to a Layer 2 switchport. Which means when you reload your switch with IOS XE 16.11.1, your switchports will be in a Layer 2 switchport state by default. This will break your routed infrastructure if you do not perform the pre-installation tasks!

The reason for this changes is to enable day 0 discovery when using Cisco Digital Network Architecture (DNA) Center (or Cisco DNA Center).

You have the option to change the L2 interfaces back to L3 by performing this manually or scripted. It’s completely up to you how you handle this step but Cisco does provide a step by step guide on how to script this procedure.

Below is the release notes for this version which includes the pre-installation procedures to ensure that after a reboot your Layer 3 ports maintain their Layer 3 state.

I will try to get my hands on a 9500 to perform this and will report it here. For the mean time please refer to the below.

IOS XE Gibralter 16.11.1 Release Notes

Mike