export const netMaskFromCidr4 = (cidr: number) => {
  const mask = [];
  let bitCount = cidr;
  for(let i=0; i<4; i++) {
    const n = Math.min(bitCount, 8);
    mask.push(256 - Math.pow(2, 8-n));
    bitCount -= n;
  }
  return mask.join('.');
};