Dynamic IP address assignment on the DHCP server side.
What is Port 67 used for?
UDP port 67 is commonly used by the DHCP server to receive client requests and return the network parameters required for configuration.
Role and operation
A DHCP client normally uses UDP 68 and contacts the server on UDP 67. During the DORA process, the client sends messages such as DHCPDISCOVER and DHCPREQUEST, while the server replies with DHCPOFFER and DHCPACK. Because the client may not yet have an IP address, initial exchanges can use broadcast. A DHCP relay can forward these messages between subnets and the server.
Transport protocol
UDP
Security precautions
Should this port be opened in the firewall?
Allow UDP 67 only between the relevant clients or relays and legitimate DHCP servers. Between VLANs, permit the flow only when the design uses a DHCP relay and restrict sources, destinations, and interfaces to what is required.
How can this port be checked?
Trigger a DHCP renewal on a client with ipconfig /release followed by ipconfig /renew, review leases and server logs, and use a packet capture filter such as udp.port == 67 || udp.port == 68. Also verify the DHCP relay configuration when the client and server are on different subnets.
Test-NetConnection -Port tests TCP and therefore does not validate UDP 67. For DHCP, use an actual lease exchange, logs, and packet capture.