Generally, in perimeter control, congestion from inside the reservoir ismoved to the outside by manipulating the inflows which create queue. As in our settings, one of the routes have an alternative route (freeway), the total input demand of the network is distributed along the transfer route and a freeway. To solve the problem of demand flow distribution, in this work we applied a routing discipline corresponding to user equilibrium (UE). Therefore, drivers can choose a route with lower travel time that is no longer crossing the reservoir. Doing so, we are not only considering the side-effects of perimeter gating control in terms of congestion but we are also taking into account the external user adaptation to it. The main contribution of this paper compared to previous works is that the external UE discipline makes the input demand elastic from the reservoir point of view. The evaluation of the global system performance is then much more realistic. Note that the way we implement that external UE discipline with the MFD framework is also a contribution by itself. Further, we analyze the impact of routing on perimeter gating control and sheds some light on the side-effects (in terms of the queue, emissions, and total time spent) of perimeter gating control.