Looking for advice on securing Wired Networks

At my company, we build short term networks at event venues all across the world.

We take our own badge printing systems to these venues, which basically comprise of laptops and label printers. As a result of this, we have the same basic template for everywhere, but the unique requirement of each event determines the size and complexity of the network.

The venue in question will typically provide us with 2 services. The first is our connection the internet. We usually bring along a small router, something like an EdgerouterX, which gets a DHCP address from the venue network, and our router does NAT from there. The second service they provide will be a link to connect two or more areas of their venue together. This is the part that we want to secure.

The goals of this link is to provide the same Layer 2 Network at either end of it. It is up to the venue network provider to determine exactly how this happens but probably one of the following:

* Literally just a cable ran end to end * A simple loop through their patch panel * They use some simple unmanaged switch that only has our connections on it * They segregate our connections into a single VLAN that is otherwise "empty"

What we are looking for is some way of securing our connection through these links, as we cannot trust it. I've looked at MACsec, but I think due to the limitation where we don't know how the network functions between our two areas, this might not be possible.