Ukraine Always Get What You Want

Maybe this is a down-and-dirty answer.

That is a reaction to the news, so I would wait till things shake out to see exactly what teeth the sanctions on its central bank will really have.

Russia has probably about a trillion dollars in foreign currency reserves. But only about $300 billion of it would be trapped in the west between foreign currency swaps and deposits in foreign banks.

That means they still have a lot of liquid assets on hand. It's a substantial cushion with which to prop up the ruble. Just from what their central bank has released, they are sitting on more than 320 billion euros, another 160 billion in dollars, 70 billion in British pounds, 130 billion in Chinese yuan, at least $220 billion worth of gold (and they have been the most aggressive buyer over the last 10 years or so), and smatterings of holdings in other currencies.