Your router has to support relaying DHCP requests to MPLS VPNs (DHCP relay = option . MPLS operates 'under' any particular protocol, if you will, so DHCP shouldn't be a problem. Taken from Cisco's documentation
In some environments, a relay agent resides in a network element that also has access to one or more Multiprotocol Label Switching (MPLS) virtual private networks (VPNs). If a DHCP server wants to offer service to DHCP clients on those different VPNs, the DHCP server needs to know the VPN in which each client resides. The network element that contains the relay agent typically knows about the VPN association of the DHCP client and includes this information in the relay agent information option.
The DHCP relay agent forwards this necessary VPN-related information to the DHCP server using the following three suboptions of the DHCP relay agent information option:
•Server identifier override
You also get the potential benefit of using the same address pool(s) for different remote branches, b/c every packet forwarded by the router contains the VPNID that the request originated from.