The DHCP relay capability provided by NSX in your vCloud Director environment enables you to leverage your existing DHCP infrastructure from within your vCloud Director environment without any interruption to the IP address management in your existing DHCP infrastructure. DHCP messages are relayed from virtual machines to the designated DHCP servers in your physical DHCP infrastructure, which allows IP addresses controlled by the NSX software to continue to be in synch with IP addresses in the rest of your DHCP-controlled environments.
The edge gateway's DHCP relay configuration can list several DHCP servers. Requests are sent to all listed servers. While relaying the DHCP request from the VMs, the edge gateway adds a gateway IP address to the request. The external DHCP server uses this gateway address to match a pool and allocate an IP address for the request. The gateway address must belong to a subnet of the edge gateway's interface.
You can specify a different DHCP server for each edge gateway and can configure multiple DHCP servers on each edge gateway to provide support for multiple IP domains.
DHCP relay does not support overlapping IP address spaces.
DHCP relay and DHCP service cannot run on the same vNIC at the same time. If a relay agent is configured on a vNIC, a DHCP pool cannot be configured on the subnets of that vNIC. See the NSX Administration Guide for details.