Russia has declared the aim to close its national network from the global Internet. This could cause a situation where the rest of the `open network society' is forced or wish to consider closing their national networks as well. A situation where national governments restrict substantially the information flows and connectivity of the network could cause serious effects to the critical infrastructure, economy, and alliances. This paper proposes a wargaming framework to analyze the effects of closing the national network on hostile actors operating critical infrastructure and who rely on the openness of that network for their operations. Our research provides information on what nations planning to close their network need to take into consideration while it offers a strategic insight for those actors who are confronted by a nation closing its network. This paper improves situation awareness and resilience in the cyber domain and supports global planning of cyber operations and defense.