Since the breakup of the soviet union, Russia has invaded two nations: Georgia and the Ukraine. It invaded both for the same reason: they attempted to align themselves politically with the West and join NATO.

NATO was not founded to oppose Russian aggression. It was founded to oppose the Soviet Union. After Russia abandoned Communism, they petitioned to join NATO and the Western bloc in general. They were rejected by the West and all current hostilities stem from that rejection - Russia believed full reproachment under mutual anti-Communism was possible with the West but the West preferred their full economic subjugation.

Belarus and North Korea have been a more or less steadfast Russian allies and has never been threatened with invasion. Kazakhstan and Mongolia have maintained relatively independent political positions (playing both sides) and have never been targets of invasion. Azerbaijan has strong ties with Turkey, a NATO country, but has never attempted to join NATO itself and has friendly relations with Russia.

A NATO that includes Ukraine but not Russia is as untenable a situation as Canada having Chinese military bases lining the American border. If Canada was considering such a deal, America would invade immediately. The same would apply to Ireland hosting the Russians against the UK, or Mexico hosting the Iranians, whatever. Local rivalries are all fun and games until you start involving world power blocs. There is a reason why, despite tensions, nations like Sweden, Ireland, Canada, and Mexico do not host foreign troops; and why instances where this is threatened (the Troubles, the Cuban Missile Crisis, the Russo-Georgian war of 08) the result is always proactive invasion.