Planning for Multiple DHCP Servers
If you want to configure more than one DHCP server to manage
your IP addresses, consider the following guidelines:
Divide the pool of IP addresses so that each server is responsible for a range of addresses, and there is no overlap of responsibility.
Choose NIS+ as your data store, if available. If not, choose text files and specify a shared directory for the absolute path to the data store. The binary files data store cannot be shared.
Configure each server separately so that address ownership is allocated correctly and so that server-based macros can be automatically created.
Set up the servers to scan the options and macros in the dhcptab table at specified intervals so that the servers are using the latest information. You can use DHCP Manager to schedule automatic reading of dhcptab as described in Customizing Performance Options for the DHCP Server.
Be sure all clients can access all DHCP servers so that the servers can support one another. A client that has a valid IP address lease might try to verify its configuration or extend the lease when the server that owns the client's address is not reachable. Another server can respond to the client after the client has attempted to contact the primary server for 20 seconds. If a client requests a specific IP address, and the server that owns the address is not available, one of the other servers handles the request. In this case, the client does not receive the requested address. The client receives an IP address that is owned by the responding DHCP server.