DHCP Relay Agent

[biga]

I have a situation. A third party is going to host our desktop enviroment(VDI's). I want to create that future situation in a test enviroment in my Vmware Workstation.I'm not a networking guy.
2 Windows 2008R2 Forests with a 2 Way Transitive Forest Trust. That's setup and working.
Domain controller in both forest is DNS/DHCP server
Forest A with DC A1:
Subnet:172.16.0.0/16
GW: 172.16.1.10
Forest B with DC B1:
Subnet: 10.10.10.0/24
Gateway:10.10.10.1
Router:
OPNsense offcourse :-)
Lan(Forest A):172.16.1.10
WAN: DHCP
Trust(Forest B): 10.10.10.1
Physically the VDI clients are in Forest B, but they will be joined in the Active Directory of Forest A(DC A1)
VDI clients needs to be in the same subnet as Forest A.(I think)
DHCP server in Forest B needs to serve 10.10.10.0/24 and 172.16.0.0/16 subnet.
Do i have to do some kind of subnetting? Create Vlans? Use DHCP relay agent in OPNsense?How to configure the DHCP server to support multiple subnets?
Thanks

[GreG.P.]

Hi Biga,

First, VDI's Clients doesn't need to be in the same network that the DHCP servers or Domain.
If VDI's clients are in different network of DHCP servers, you need to relay the DHCP request.
The DHCP relay service offer to do this by transforming the multicast request to an unicast request.
This is working to deserve several subnets to one or several DHCP servers (for load balancing or fault tolerance).
In this case, if you have several vlan configured (one for each VDI's clients), you need to activate DHCP relay service with indicate theIP adresses of DHCP server(s) and all VDI's clients networks.
The router (or switch) configured with DHCP relay need to have one network interface in each clients' subnets and one interface in the DHCP servers subnet. By default a DHCP relay are listen on all network interfaces but I suggest you to limit only to clients computers network.
The DHCP server will offer the correct Network configuration for clients because the network source is know by the router.