While i agree with this statement, it is only relevant when those NIC’s are activated at same time…
Otherwise the router should be able to fix the routing automatically because it will only see one of the NIC’s…
This topic is so confused by the OP’ers provided info and wording, which makes us confused just as much as like the router is in this case with the NIC’s
The topic started as a “404” problem, then evolved into an IP problem, just wait till it evolvs into a “Bonding” problem where the OP explains that it actually wanted to use both wired and wireless at same time…