dhcp

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on IP networks to automate the assignment of IP addresses and other network configuration parameters to devices. DHCP simplifies administration by centralizing address allocation and reducing configuration errors. A DHCP client obtains its settings from a DHCP server, typically during boot, via a four-step exchange known as DORA: Discover, Offer, Request, and Acknowledgement.

DHCP can operate across multiple subnets using a DHCP relay agent, which relays messages between clients and servers that are not on the same broadcast domain. A DHCP server maintains a pool of available IP addresses and can assign options such as subnet mask, default gateway, DNS servers, domain name, and lease duration. The client leases an IP address for a defined period, after which it must renew the lease or obtain a new one.

DHCP supports IPv4 through DHCPv4 and IPv6 through DHCPv6. In IPv6 networks, addresses may be assigned by SLAAC or via stateful DHCPv6, or a combination of both. DHCP options allow servers to convey configuration parameters beyond the address, including NTP servers, WINS, or vendor-specific settings.

Management features include address reservations (static mappings), excluded addresses, and scopes or pools. DHCP failover and load sharing provide redundancy. Security considerations include DHCP snooping and the fact that DHCP does not include built-in authentication; trusted-relay configurations help mitigate attacks.

DHCP uses User Datagram Protocol ports 67 (server) and 68 (client). It is widely used in enterprise networks and home networks to streamline device onboarding and ensure consistent network configuration.