code: public static NetworkAddress parseBlock(String networkAddress) {
  		NetworkAddress address = null;
  		if (networkAddress != null) {
  			String[] split = networkAddress.split("/");
  			if (split.length == 2) {
  				byte[] network = parseDottedQuad(split[0]);
                  byte bits = Byte.parseByte(split[1]);
  
  				address = toNetworkAddress(network, toNetworkMask(bits));
  
  
  			}
  			else {
  				throw new IllegalArgumentException("Network address must be ip4Address/prefixSize");
  			}
  		}
  		return address;
  	}
docs: parse a CIDR network block identifier, consisting of an ip4Address/prefixSize, where both ip4Address and netMask are
  presented in dotted quad notation.  e.g. 192.0.2.0/24
  @return
  @see {http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#IPv4_CIDR_blocks}