When you have more than one subnet on the same physical network, you need to give some thought to broadcast addresses. According to the latest standards, there are two different ways for a host on subnet 128.6.20 to send a broadcast on the local network. One is to use address 128.6.20.255. The other is to [...]

There is another way to handle several subnets on one physical network. This method involves intentionally misconfiguring your hosts, so it is potentially dangerous if you don’t watch what you are doing. However it may be easier to deal with when you have lots of subnets on one physical network. An example of this is [...]

Most software is written under the assumption that every computer on the local network has the same subnet number. When traffic is being sent to a machine with a different subnet number, the software will generally expect to find a gateway to handle forwarding to that subnet. Let’s look at the implications. Suppose subnets 128.6.19 [...]

Suppose that you have been convinced that it’s a good idea to impose some structure on your addresses. The next question is what that structure should be. There are two basic approaches. One is subnets. The other is multiple network numbers.
The Internet standards specify the format of an address. For addresses beginning with 128 through [...]

It is not necessary to use subnets at all. There are network technologies that allow an entire campus or company to act as a single large logical Ethernet, so that no internal routing is necessary. If you use this technology, then you do not need to subdivide your address space. In that case, the only [...]

The first comment to make about addresses is a warning: Before you start using an IP network, you must get one or more official network numbers. IP addresses look like this: 128.6.4.3. This address is used by one computer at Rutgers University. The first part of it, 128.6, is a network number, allocated to Rutgers [...]