There doesn't seem to be a way to simulate a VPN peer initiating a IKE negotiation to your Check Point firewall, at least that I can see. Once the tunnel is up (no matter who initiated it) it is a two-way street, but in an interoperable scenario sometimes there will be a IKEv1 Phase 2 subnet/Proxy-ID negotation failure if one side initiates the tunnel, but the other side can initiate it just fine. Not much you can really do about this except have the VPN peer try to initiate to you and see what happens.
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