title: Creating an IPv6 subnet with 64 bits prefix
body: <p>I'm having a look at this <a href="http://www.subnetonline.com/pages/subnet-calculators/ipv6-subnet-calculator.php" rel="nofollow">IPv6 calculator</a> to learn how IPv6 subnets work, however there's something I don't understand.</p>
  
  <p>I'm trying to create one subnet with address:</p>
  
  <pre><code>2001:db8:8714:3a90:/64
  </code></pre>
  
  <p>When I do so it tells me that 1 bit is required and that 63 bits are remaining, which makes sense. However, when I click on "Calculate subnet", it tells me:</p>
  
  <blockquote>
    <p>Error: You do not have enough room for this many subnet levels with this prefix. Remove some subnet levels or increase the prefix and try again.</p>
  </blockquote>
  
  <p>This is the part I don't get. With 64 bits available, there should be more than enough for a subnet, or am I missing something about the way IPv6 subnetting work?</p>