DHCP Request message sent as broadcast

During the DHCP DORA process various DHCP messages are exchanged between the DHCP server and the clients. The DHCPREQUEST message is the message the client sends to the DHCP server in response to the DHCPOFFER message.

This message is typically sent as a broadcast using the broadcast MAC address. However, because at this point, the client typically knows the MAC address of the DHCP server, an optional client behavior, request messages may be replaced with unicasts. But this is up to the implementation of the specific vendor or operating system of the device.

For clients requesting the renewal of an existing lease, they will typically communicate directly via UDP unicast since the client already has an established IP address at that point.

Links

https://networklessons.com/cisco/ccie-enterprise-infrastructure/introduction-to-dhcp

https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#Request