Windows DHCP server with scope on different subnet

You have to configure "ip forwarder" so it forwards DHCP requests to the different subnet.

Can you elaborate please? Is this something I have to do ie on the Sonicwall?

Also, do I need any addition DHCP server config? My case is similar to a DHCP with multiple scopes (except there is only one scope). How does the server know to assign an address from a subnet it doesn't belong to?

Yes, Sonicwall seems to be working as a router in your network, so yes, you have to configure it.

Did you assign more than one IP to the nic on the DHCP server?

Yes.  You'll have to configure this on the Sonicwall.

DHCP works via broadcasts.  DHCP clients send out broadcasts asking for a DHCP server to respond with an IP.

Routers block broadcasts... they do not forward them to the other subnets for which they are routing.

So, you have to set up an "ip helper" on the interfaces of the router.  These are DHCP proxies that forward DHCP broadcasts (and only DHCP) to the DHCP server so it can respond.

Also, keep in mind you'll have to create a second DHCP scope on your DHCP server for the second subnet.

I found some Sonicwall documentation and setup IP Helper but no luck. Do I need any addition DHCP server config? My case is similar to a DHCP with multiple scopes (except there is only one scope). How does the server know to assign an address from a subnet it doesn't belong to?

As I mentioned, you'll need a second DHCP scope for the second subnet.

Can you post some config info?  LIke what are the network IDs of the two subnets?

The server should know it based on vlan.

I only have one (default) VLAN on the Netgear. DHCP server is 10.38.50.61/24. DHCP range is 10.38.1.xx/24. Sonicwall interface listens to both 10.38.50.1 and 10.38.1.1.

You will have to have a DHCP scope for each of the 10.38.50.0 and 10.38.1.0 subnets.

I don't need DHCP scope for the 10.38.50.xx. I only need it for 10.38.1.xx.

If you want to do this from what info you've given -
Add either a second nic on the server for the other subnet or add a second IP to the existing nic - provided everything that isn't going to use the DHCP has a static IP.

You could also do vlans and have multiple subnets on the dhcp server.

Sorry... I misunderstood.

So, the servers are on .50 and the clients are on .1.

For that, you should only need to configure a scope for the clients.  The scope would have to be for their network ID, so 10.38.1.0/24 with the appropriate options configured for their subnet.

On the Sonicwall, you'll need to configure an IP helper address on the interface for 10.38.1.0/24 and point it to the DHCP server address of 10.38.50.61.

This is assuming you've created VLANs or have in some other way configured the two subnets to be physically (or in the case of VLANs, logically) separated from each other.

Hi There,

10.38.50.x: Server subnet
10.38.1.x: client subnet

Netgear switch: Plain L2 where clients are connected.

Kindly confirm if you have defined vlans anywhere and enabled intervlan routing.
If not, kindly confirm if the server subnet and the client subnet are able to reach other (check from a sample workstation).

Below link will help you in defining IP helper address on Sonic wall:
http://help.mysonicwall.com/sw/eng/7630/ui2/70/Policies_Network_IPHelper_Snwls.html.

You need DHCP relaying :
https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#DHCP_relaying

And a scope that matches the subnet for your clients.

That's all.

Thanks for the replies, I know understand what my options are!