OpenBSD's DHCP server, dhcpd, implements the Dynamic Host Configuration Protocol (DHCP) [1] and the Internet Bootstrap Protocol (BOOTP) [2]. DHCP allows hosts on a TCP/IP network to request and be assigned IP addresses, and also to discover information about the network to which they are attached. BOOTP provides similar functionality, with certain restrictions. The DHCP protocol allows a host which is unknown to the network administrator to be automatically assigned a new IP address out of a pool of IP addresses for its network. In order for this to work, the network administrator allocates address pools in each subnet and enters them into the dhcpd's configuration file. OpenBSD's implementation of the DHCP server is based on an early version of ISC's dhcpd that the OpenBSD project further developed to incorporate additional security features such as privilege separation and the ability to synchronize provisioning of IP addresses to clients with updates to PF firewall filtering rules to effectively implement egress and ingress filtering based on live client IP addresses on the network served by dhcpd.
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