Setup

My setup looks like this:

• Work laptop connected to Dell U3421WE with a single USB-C cable
• Personal laptop connected to a Thunderbolt3 Dock with a single USB-C cable. The Thunderbolt3 Dock is connected to Dell U3421WE with DP and USB-B cables
• Keyboard, mouse, and Ethernet cable connected to Dell U3421WE

[Work laptop] --USB-C--> [U3421WE] <--DP+USB-B-- [Thunderbolt3 Dock] <--USB-C-- [Personal Laptop]

Problem

Usually I'm running both laptops in a PBP setup and have a "Switch USB" keyboard shortcut that allows me to change which laptop I am controlling. When switching USB, apart from the keyboard and mouse, the Ethernet is passed to the other laptop as well (which makes sense as I'm assuming the monitor is acting as a Dock).

The problem is that when switching USB, the network connection drops for a few seconds until the first laptop establishes a new connection via WiFi. I'm often connected to a VPN on my work laptop, and the connection drop makes me lose my VPN connection (which causes other issues).

Question

Is there a way to make the Dell U3421WE deliver Ethernet only through the USB-C cable in such a way that "Switch USB"  does not pass control of the Ethernet to the other laptop?