Motherboard Intel D410PL, one nic on board and second nic plugged to PCI (Realtek rtl8193D).
After fresh installation, i detect of two nic's have same MAC address (as external).
And if plug Gigabit Ethernet, change MAC address manualy network work.
If plug Fast Ethernet, change MAC address manualy, network not work.
This problem produce on any count of this motherboard model.
If plug Intel NIC, this problem not appear and mac addresses separated.
In some cases carrier status react only from one nic to two.
In forum i create thread https://forums.freebsd.org/threads/57323/
If need additional information, i can post it here, thanks.