doubt Implementation

Good morning everyone,

I know that perhaps my doubt is simple, but it's always good to ask.

I have a scenario of a client that looks like this:

It has a dedicated link

This dedicated link is connected to a Dlink router simple

and router ip station in the station of work and his main DC server.

I'll have to install forefront tmg this client, the problem is that it needs to use the D-link router because the wireless.

So I wanted to know how to proceed:

1 - I get the ip of the router and use in forefront tmg on board rede_internet?

or

2 - I turn on the cable network that the dedicated link directly to TMG server on the external network card?

How should I proceed?

Only exemplifying the scenario:

Dedicated link on the router d-link router d-link connecting the workstations to provide the internet.

I have to fit tmg this process, what is the best practice and output?