# File lib/ec2/right_ec2_vpc.rb, line 128
    def create_subnet(vpc_id, cidr_block, availability_zone = nil)
      request_hash = { 'VpcId'     => vpc_id,
                       'CidrBlock' => cidr_block }
      request_hash['AvailabilityZone'] = availability_zone unless availability_zone.blank?
      link = generate_request("CreateSubnet", request_hash)
      request_info(link, QEc2DescribeSubnetsParser.new(:logger => @logger)).first
    rescue Exception
      on_exception
    end