Enabling DHCP Support for Multiple Subnets

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

If you have multiple subnets in your network, and do not have a DHCP server on every subnet, determine whether your current routers relay DHCP/BOOTP messages.

If your routers cannot be used for DHCP/BOOTP relay, set up a DHCP/BOOTP relay agent on at least one computer running Windows Server 2003 on each subnet. The DHCP/BOOTP relay agent relays DHCP and BOOTP message traffic between the DHCP-enabled clients on the local network and a remote DHCP server located on another physical network by using the IP address of the remote DHCP server.

Figure 2.3 shows a simple, routed network in which the router acts as a DHCP relay agent.

Figure 2.3   Subnets Configured to Use a DHCP Relay Agent

Subnets Configured to Use a DHCP Relay Agent

If your routers cannot be used for DHCP/BOOTP relay and you choose not to configure DHCP/BOOTP relay agents, you must configure your network so that a DHCP server has a network adapter on each subnet it serves. You can accomplish this by either placing a DHCP server on each subnet, or by multihoming DHCP servers. This distributed configuration does not provide fault tolerance. If a DHCP server becomes unavailable, DHCP clients on the subnet cannot receive IP addresses and options.


  • The DHCP Relay Agent service is available only on computers running Windows Server 2003, Microsoft® Windows® 2000, or Windows NT 4.0. To use the DHCP Relay Agent routing protocol, the Routing and Remote Access service must be installed and enabled.

For more information about installing and configuring DHCP relay agents, see "Configure the DHCP Relay Agent" in Help and Support Center for Windows Server 2003. For more information about the DHCP Relay Agent service, see the Networking Collection of the Windows Server 2003 Technical Reference (or see the Networking Collection on the Web at https://www.microsoft.com/reskit) or see Help and Support Center for Windows Server 2003.