Monitoring node with npath routing

Apologies for the late reply hexueli. I've been on holiday. We are using LTM only with n-path otherwise known as Direct Server Return. The problem I had was not with the F5 devices but with the way I was configuring my RHEL 5 Linux boxes to accept packets for the VIP. The command included above was what I was using to configure the VIP as an interface IP on the Linux boxes. As someone else stated above, the correct LTM monitor configuration should set Transparent to YES and specify an Alias IP of whatever the virtual service IP is.