hm that is rather few information.
Basically the routing gives the way. So first of all there must be a route that matches the destination. Secondly there has to be a policy to allow the traffic.
If destination is a physical,vlan or switch interface you don't need explicite static routing since these automagically create a "connected" route with them.
In these cases you just need some policy to allow the traffic to flow :)
All other cases require explicit static routing.
Alas the VPN itself will listen on the interface you selected when you created it.
This is only used for the VPN itself (transport + encryption).
The rest as said is given by the routing and policies.
Could you explan you problems a bit more detailed then?
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