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I am trying to configure a Windows 2019 RRAS VPN server to use DHCP for VPN address assignment from a specific network.

RRAS VPN Server - 192.168.1.20

DHCP Server - 192.168.1.10

VPN Network / Scope - 192.168.10.0 /24

My DHCP server is located on the same network as the VPN server but the IP addresses I want to assign to my VPN clients are that of another network (192.168.10.0/24). These servers are virtual machines running on Hyper-V (on the same host). The DHCP server has multiple scopes configured to serve the physical VLANs in our office. The DHCP server knows which scope to assign addresses to these VLANs from due to IP helper addresses on the physical switches.

How can I configure RRAS on the VPN server to request addresses from the 192.168.10.0/24 scope on the DHCP server?

At the moment, the VPN server is on the 192.168.1.0/24 network (the same network as the DHCP server). If a VPN client connects, it will send out a DHCP request to the DHCP server but how do I control which scope it receives an address from?

I want it to receive a 192.168.10.xxx address and not an address from any of the other scopes being served by that DHCP server. Is this possible with RRAS and Hyper-V virtual switching?

Any help appreciated.

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You can, using the RRAS MMC Snap-In and a DHCP Relay.

To configure RRAS to use addresses from a DHCP server

  1. Open the RRAS MMC Snap-in.
  2. Right-click the RRAS server name, and then click Properties. If you are using Server Manager, right-click Routing and Remote Access, and then click Properties.
  3. On the Properties page, click the IPv4 tab.
  4. Under IPv4 address assignment, click Dynamic Host Configuration Protocol (DHCP).
  5. Click OK to save your changes.

To configure the IPv4 DHCP relay agent

  1. Open the RRAS MMC Snap-in.
  2. In the Routing and Remote Access MMC snap-in, expand IPv4, and then click DHCP Relay Agent.
  3. Add the network interfaces on which the server might receive DHCP requests that you want to send to the DHCP server. Right-click DHCP Relay Agent, click New Interface, select the appropriate network interface, and then click OK.
  4. In the DHCP Relay Properties dialog box, select Relay DHCP packets, and then click OK.
  5. In the navigation pane, right-click DHCP Relay Agent, and then click Properties.
  6. On the General tab, enter the IPv4 address of the DHCP servers that you want to provide DHCP services for the RRAS server’s clients, click Add, and then click OK.
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  • Thanks for the reply Chris. So I will need a second NIC to use as the DHCP Relay? Presumably I just configure this NIC with an address on the network/scope that I want the VPN clients to receive addresses from? For example, if I give the additional NIC the IP address of 192.168.10.10, the DHCP server will know to give the VPN clients an address from the 192.168.10.0 /24 network/scope? – OliverPG Aug 12 '20 at 21:53
  • It is best practice to setup a RRAS server with a second NIC. Don't forget to create a static route to allow traffic from the VPN subnet to reach your internal services. – Christopher H Aug 12 '20 at 22:11

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