It is a good idea to split a scope between two or three servers. In this way, one can handle DHCP traffic flood more easily. In addition, if a server fails, the network is not affected. An 80/20 split seems to offer the optimum benefit.
For example, consider a Class B scope 132.255.0.0 with address range from 132.255.0.1-132.255.255.255 and subnet mask 255.255.0.0. One setup would be to distribute the load between two servers (SRV1 and SRV2). SRV1 has a scope of 132.255.0.1-132.255.255.255 with a mask of 255.255.0.0. The exclusion range for this scope is 132.255.128.0-132.255.255.255. SRV2 has a scope of 132.255.0.1-132.255.255.255 with a mask of 255.255.0.0. The exclusion range for this scope is 132.255.0.1-132.127.255.255. A scope can also be divided between three servers in a similar way.
Additional Resources
For a list of Help topics providing related information, see Recommended tasks for the DHCP server role.
For updated detailed IT pro information about DHCP, see the Windows Server® 2008 documentation on the