On a Raspberry Pi model 1 'B', using the RC1 version of FreeBSD 11.0
following 'poweroff' and 'shutdown', when the message that the system has halted appears on the serial console, the network interface is still active and responds to 'ping' with the same IPv4 address as was assigned by DHCP. This makes it difficult to determine when it is safe to power off the Raspberry Pi on a headless system. (Normally you could just wait a certain time period following the network LEDs turning off)
This happens whether or not a serial console is present. I added the serial console so I could determine whether or not shutdown and poweroff were executing properly, and determined that it was, except for not disabling the network adaptor.