open a terminal and type su
type ifconfig and then you should see your machines ip address
type route
make sure the ipaddress is on the same lan as the gateway
you should have three lines one marked as ug the default gateway.
If you are using a router make sure you can see it's setup page
go and ensure the dmz is not ticked
If you go to Yast you can set these again under network choosing your device to connect to the internet.