DHCPi

DHCPi is not a formal standard in the official DHCP specifications. In some documentation and vendor materials, the term DHCPi is used informally to refer to the DHCP Inform operation, or more broadly to information-request behavior within the DHCP protocol family. The core IPv4 DHCP specification (RFC 2131) defines a DHCPINFORM message type, used by a client that already has an IP address to request additional local configuration parameters from a DHCP server. In IPv6, DHCP is defined separately (DHCPv6), which has its own message flows and information mechanisms; the explicit term DHCPi is not codified in the RFCs for DHCPv6.

Operation and purpose

In an information-request scenario, the client already holds an IP address (obtained by some means other than the current server) and sends a DHCPINFORM message to a DHCP server to obtain configuration options such as DNS servers, NTP servers, or vendor-specific options. The server replies with a DHCPACK containing the requested options, and no new IP address is issued or leased during this exchange. This makes DHCPINFORM useful for devices that require only configuration parameters or for network boot scenarios where an IP address has been assigned statically or by another mechanism.

Use cases and considerations

DHCP Inform is commonly used when a device obtains an IP address through another method (static assignment, IPv4 link-local, or previous DHCP lease) but still needs network configuration parameters provided by a DHCP server. Security considerations include the absence of strong authentication by default, which can lead to spoofed responses if not mitigated by network controls. Proper server authorization and network segmentation are recommended to prevent misconfiguration or exploitation.

See also

DHCP, DHCPINFORM, DHCPv4, DHCPv6, Information-Request (in DHCPv6 context)

References

RFC 2131 (Dynamic Host Configuration Protocol).