code: public static Ipv6Range parseCidr(String cidrString) {
          int idx = cidrString.indexOf(SLASH);
          Validate.isTrue(idx != -1, "Argument [" + cidrString + "] is not a range or does not comply with the CIDR notation");
          String address = cidrString.substring(0, idx);
          String prefix = cidrString.substring(idx + 1, cidrString.length());
          return Ipv6Range.from(address).andPrefixLength(prefix);
      }
docs: Parses a <tt>String</tt> of an IPv6 address and its subnet mask formatted as in a
  Classless Inter-Domain Routing (CIDR) notation.
  
  @param cidrString a CIDR-notation string, e.g. "2001:0db8:0:cd30::/60"
  @return a new {@link Ipv6Range}
  @throws IllegalArgumentException if the string cannot be parsed
  @see <a href="http://tools.ietf.org/html/rfc4632">rfc4632</a>
  @see <a href="http://tools.ietf.org/html/rfc4291#section-2.3">rfc4291 §2.3</a>