DHCP Servers and Placement

The number of DHCP servers you need on a network is driven by the number of clients, availability requirements for the DHCP server, and the network topology. The number of clients a DHCP server can serve varies based on the hardware of the server and whether it provides multiple roles or is strictly a DHCP server. Most can provide IP addresses to thousands of hosts. Server hardware that will have the greatest impact on DHCP performance includes the network interface and hard disk. The faster the network interface card (NIC) and disk access, the better. In addition, multiple NICs will greatly improve performance, since NIC speed in no way compares to the speed of the internal PC hardware, and adding NICs literally relieves a bottleneck.

The availability of the DHCP services to the network drives multiple DHCP servers. You must have at least two DHCP servers. You might want to cluster the server if you have a large scope of addresses that are provided to a network segment.

The network topology will drive additional servers as well. This is something that must be reviewed and then planned. Ideally, a network should have a DHCP server on each segment, although this becomes impractical. Because you can configure routers to forward DHCP requests using a DHCP Relay Agent, you can place DHCP servers at any location on the network. Therefore, you should probably look at the unstable WAN links as the deciding factors for additional DHCP servers. A network that has a highly unstable satellite link to a location that has thousands of clients will require its own DHCP server. However, a network with a highly unstable satellite link to a location that has only a few clients will probably be better served by a statically applied IP address or alternate IP configuration used with DHCP from across the link.

Source of Information : Syngress The Best Damn Windows Server 2008 Book Period 2nd Edition