Can traefik forward http request to host interface eth1?

Can traefik forward a request to an host interface eth0, vmnet1, vobxnet0 instead of a docker service.
Would like to use traefik to forward requests to docker services and virtual machines on the same host.

I'm not sure I understand the question http protocol level interactions are unaware of network interfaces. To me the phrase "forward http request to host interface eth1" is internally inconsistent, it's asking about something that is impossible intrinsically, like dry water in colloquial sense.

Traefik will forward requests to any url that you specify. If you can specify a url that ends up where you want it to end up calling from where traefik sits it will work. Traefik itself does not work any more at network interface level than most of any other network connected applications.

Can traefik match a rule and route a request to an IP address on a host interface ?
I would like to use traefik to forward requests to my containers and virtual machines that live on the same host as traefik.

Traefik can redirect request to any url that you specify. Ususally urls include symbolic names that are resolved via DNS to ip addresses, but they can also use ip addressed directly. Note, that in this case TLS would most likely break, as it's rare for web TLS certificates to be issued to an IP address.

If any other application running at the same place as traefik can reach the url you are interested in, traefik will be able to reach this url too. If your networking infrastructure / setup prohibits this access to it, then traefik won't be able to reach it either. Traefik itself does not have capabilities to manage your network infrastructure, you need to set it up first, for trafik to use.

For example, frontend is fowarded to backend
The backend is a virtual machine interface on the same host as traefik.
Since labels cannot be used like they are when creating containers, how would this be configured in the toml file ?

It sounds like you want an application in a docker container to be able to reach a certain destination. Can you explain, how you configure this, without traefik? That same configuration should naturally work for traefik too, and to me it sounds like it does not matter if you use labels or toml file for that.

The first question you need to answer is how do you do this in principle, without traefik, and then work it out from there.

I have a server with a virtual machine running that i can ssh into.
I would like traefik to run on the same server and forward requests for to the virtual machine.