Did you check DHCP-disposed address on the router-connected NIC? Is there any probability that it resides in the same IP segment – 192.100.100.x ?
ipconfig /all in the cmd window should provide this information. If both IPs start with 192.100.100., you should change the settings of the configuration of router’s DHCP server so that addresses it disposes are in a different segment, e.g. in 192.100.1.x
This kind of problem is the first thing which should be checked, then one should check the hardware…