3.3.4.1 Sending a DHCPINFORM Message
A Validating Server MUST open UDP port 68 on the interfaces bound to the DHCPv4 server. If the server does not contain bound interfaces, the server cannot validate itself.
A Validating Server MUST send a broadcast DHCPINFORM message to address 255.255.255.255 with the Rogue Detection Request Option (section 2.2.2.4) on all the interfaces bound to the DHCPv4 server.