Where will the DHCP subnet be obtained from if there is a two NSG devices with a Site-To-Site VPN?

Zyxel_Chris

The client still use the local LAN subnet to communicate with the peer site, so it won't get the IP from the peer site DHCP server.

For instance, there are 2 NSG connected with site-to-site VPN as like the following topology. The client under NSGA is still using LAN1 subnet 192.168.10.0/24 to communicate with LAN2 subnet 192.168.20.0/24.

LAN1--(192.168.10.0/24)NSG(A)===VPN===NSG(B)--LAN2(192.168.20.0/24)