There are many posts saying to move the MAC address of an eth3 or similar to eth0 to get the DNS settings and features of eth0. For example, I have my Mellanox 10G-SFP card connected via DAC and working over 10G link, pulling an IP with no issue in unRAID. It's marked as eth4, and when it is connected while eth0 is not (1GBE), DNS issues occur, because unRAID does not allow eth4 to get the DNS server from the DHCP server.   No problem. Re-assign eth4's MAC to eth0 in the Interface List