LTM ip forwarding for outbound traffic over two gateways

Hi, I configured a LTM in my lab as a forward proxy for outbound traffic. The vs uses a gateway pool which contains two gateways (linux based in ip forwarding mode). This pool is also the default gateway for the BIG-IP itself. I configured on the pool "action on service down" and set it to "reselect". The problem is when I open a wget session on a client that uses the vs for downloading an iso file from the internet the session is just ready as long as the specific gateway pool member is available. If the specific pool member goes down for some reason the session will be broken. How is it possible to configure LTM in load balance per packet mode? Thank you, bb