wireless interface vs wired interface

hello:

i have been using opensuse 13.2 on an old t60 for over a year. it has both wired and wireless interfaces. for quite a long time i was using wired only until a month ago i activated wireless. it works fine in the environment with no wired connections. to my surprise, now the traffic would not use wired connection any more, it is always on wireless. even wired connection is there.

i had tried to shut the wls3 down by “sudo ifconfig wls3 down”, but traffic went nowhere; wired interface just didn’t pick up the traffic at all.

i thought it should behave like wintel machine: as long as wired connection is active, it will prefer wired connection until wired interface down. are there any ways to fix this?

thanks.

_dave