As far as I can see, you already have a default route. That is why you are getting that error. Your default route is the following:
default dev venet0 scope link
You must change it instead of adding a new one. Try this:
[root@marketport tmp]# ip route change default via <gateway ip> dev venet0 src <your ip>
Last edited by lsalab; 07-01-2014 at 04:34 PM.