Skip to main content
Home DHCID record

DHCID record

(also DHCP Identifier record)

DHCID record definition

A DHCID record is a specialized type of DNS record that binds a DNS name to a unique client identity as seen by the DHCP (Dynamic Host Configuration Protocol) server. It is most often used where hostnames and IP address assignments are rapid and managed automatically — for example, in networks with a high device turnover. 

When a device receives an IP address from the DHCP server and requests that a DNS record be created with its hostname, the DHCID record verifies the request’s legitimacy (that is, it checks if it is not overwriting DNS information that belongs to another device). The DHCID record contains a cryptographically generated identifier derived from information unique to the DHCP client, such as the latter’s MAC address. 

See also: DNS resolution, DNS, DNS redirection, DNS record, DNS query, DNS CNAME record, authoritative DNS server, DHCP

How DHCID records work

  1. 1.A DHCP client makes a DNS update request.
  2. 2.The server checks if a DHCID record exists for the hostname it wants to claim. 
  3. 3.If a DHCID record exists, the server compares the new client’s identity hash to the one stored in the record. 
  4. 4.If the identity hashes match, the update is allowed to proceed — the server has determined that it is coming from the same client. 
  5. 5.If the identity hashes do not match, the update is rejected or put on pause until administrative review.