First upgrade your X3000 to the latest firmware, like v4.7.4 stable, then log in to the router via SSH, execute this
curl -k http://127.0.0.1/rpc -H 'glinet: 1' -d '{"jsonrpc":"2.0","method":"call","params":["","netmode","set_mode",{"mode":"passthrough","mask":"auto","mac":""}],"id":1}'