 Of the three methods I'll discuss here, this is the least desirable, and the most often deployed. There are some serious problems with this method. First, there is no room for expansion in any of the subnets, except for possibly the last one used. If the sub- net 192.168.100.16 exhibits growth, and now needs 18 addresses instead of 16, the entire subnet must be renumbered to a larger subnet space elsewhere. Second, this method does not allocate addresses in a manner that allows for the largest available block to be concurrent and addressable. Another problem is future availability of subnets. Remember, with VLSM, you are not limited to having every subnet be the same size. If you plan carefully, you can use your given space very efficiently. Chapter 34: IP Design Figure 34-6 shows how we might sequentially allocate a series of /28 subnets within the 192.168.1.0/24 network. Each time we need another /28 subnet, we allocate the next one available. I've broken out the subnets to show the largest possible network space remaining after each allocation. Because we cannot use the last subnet due to the rules of networking, a lot of space is wasted. This wasted space is mostly theoret- ical, as we could always use VLSM to split the last subnet into smaller networks. But, the fact remains that by using this method, as soon as a single subnet is allocated, we can no longer assign a /25 space, as the only remaining /25 space is the broadcast subnet. 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.0/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.16/28 192.168.1.32/28 192.168.1.32/28 192.168.1.32/28 192.168.1.32/28 192.168.1.32/28 192.168.1.32/28 192.168.1.32/27 192.168.1.32/27 192.168.1.48/28 192.168.1.48/28 192.168.1.48/28 192.168.1.48/28 192.168.1.48/28 192.168.1.48/28 192.168.1.64/28 192.168.1.64/28 192.168.1.64/28 192.168.1.64/28 192.168.1.64/27 192.168.1.80/28 192.168.1.80/28 