Ok, eu só fiz isso quando eles estão em um domínio, mas você precisa desativar o DHCP no roteador, habilitá-lo no servidor (onde você pode configurar o gateway padrão, etc) ...
No roteador, deve haver uma caixa de seleção para desativar o DHCP
Installing Windows Server 2008 DHCP Server
Installing Windows Server 2008 DCHP Server is easy. DHCP Server is now a “role” of Windows Server 2008 – not a windows component as it was in the past.
To do this, you will need a Windows Server 2008 system already installed and configured with a static IP address. You will need to know your network’s IP address range, the range of IP addresses you will want to hand out to your PC clients, your DNS server IP addresses, and your default gateway. Additionally, you will want to have a plan for all subnets involved, what scopes you will want to define, and what exclusions you will want to create.
To start the DHCP installation process, you can click Add Roles from the Initial Configuration Tasks window or from Server Manager à Roles à Add Roles.
Adding a new Role in Windows Server 2008
When the Add Roles Wizard comes up, you can click Next on that screen.
Next, select that you want to add the DHCP Server Role, and click Next.
Selecting the DHCP Server Role
If you do not have a static IP address assigned on your server, you will get a warning that you should not install DHCP with a dynamic IP address.
At this point, you will begin being prompted for IP network information, scope information, and DNS information. If you only want to install DHCP server with no configured scopes or settings, you can just click Next through these questions and proceed with the installation.
On the other hand, you can optionally configure your DHCP Server during this part of the installation.
In my case, I chose to take this opportunity to configure some basic IP settings and configure my first DHCP Scope.
I was shown my network connection binding and asked to verify it, like this:
Network connection binding
What the wizard is asking is, “what interface do you want to provide DHCP services on?” I took the default and clicked Next.
Next, I entered my Parent Domain, Primary DNS Server, and Alternate DNS Server (as you see below) and clicked Next.
Entering domain and DNS information
I opted NOT to use WINS on my network and I clicked Next.
Then, I was promoted to configure a DHCP scope for the new DHCP Server. I have opted to configure an IP address range of 192.168.1.50-100 to cover the 25+ PC Clients on my local network. To do this, I clicked Add to add a new scope. As you see below, I named the Scope WBC-Local, configured the starting and ending IP addresses of 192.168.1.50-192.168.1.100, subnet mask of 255.255.255.0, default gateway of 192.168.1.1, type of subnet (wired), and activated the scope.
Adding a new DHCP Scope
Back in the Add Scope screen, I clicked Next to add the new scope (once the DHCP Server is installed).
I chose to Disable DHCPv6 stateless mode for this server and clicked Next.
Then, I confirmed my DHCP Installation Selections (on the screen below) and clicked Install.
Confirm Installation Selections
After only a few seconds, the DHCP Server was installed and I saw the window, below:
Windows Server 2008 DHCP Server Installation succeeded
I clicked Close to close the installer window, then moved on to how to manage my new DHCP Server.