DHCP over Site to Site VPN (USG40 - USG40)

pwb

Hi, i have two USG40, one in the office and one home. Site to Site VPN is function ok, but i want to have the PC at home to get IP from the USG40 at the office since that is running DHCP. I have set DHCP relay on LAN1 on the USG40 at home to point to the LAN1 ip at the USG40 at the office.

USG40 Office
LAN1 192.168.1.1/24
DHCP 192.168.1.100-200

USG40 Home
LAN1 192.168.200.1
DHCP Relay to 192.168.1.1

If i set the USG40 at home to be DHCP server and my home pc get 192.168.200.100 i can ping 192.168.1.1 and the VPN site to site is running fine. But i want the pc at home to get a ip from the local dhcp server on the office. Is it possible?

Ian31

As I know, USG doesn't support DHCP multiple scope.
So the office USG40 cannot offer the IP to your home.

But why not just use the home USG to offer the IP address ?

pwb

I need the home pc to get in the same ip range as the network on the office. But i dont need multiple scope, i need the pc at home to get a ip from the dhcp server at the office. Why is it possible to set dhcp relay as an option on LAN if its not possible to use it? Like this? The only difference is that i want to use the DHCP server thats running on the Office USG40.
https://kb.zyxel.com/KB/searchArticle!gwsViewDetail.action?articleOid=012177&lang=EN

Zyxel_Stanley

@Ian31
Really thanks for your answer of this issue.

You are correct, the USG DHCP function is only support the scope which is the same as itself network subnet. It is unable offer the IP which belonging other network subnet.

@pwb

According your scenario, the USG is unable support for your scenario.

But you can add additional DHCP server behind your office USG40.

e.g. Windows 2008R2 DHCP server.

Topology:

PC(DHCP Client)---USG40====VPN tunnel====USG40-----DHCP Server(192.168.200.34)

Windows DHCP server setting:

pwb

ok, thanks for the answer. Yes the office have a Windows server, but the one who have setup the network used the USG as the DHCP server and not the Windows server. So if i turn off the DHCP on the office USG and use the DHCP server on the Windows server then it will work? But i still find it a litle strange that i cant relay the office USG's DHCP since that on the same scope as if i use the DHCP on the server. But i will try to turn it off on the USG and on on the server and see if that work.

Zyxel_Stanley

@pwb
Yes, you can disable DHCP server function on your office USG40, and just let Windows server to offering IP address to your clients.

You just need add additional scope for your office subnet, then it will fulfill to your scenario.