Different Classes of IP Address

IP Address Classes and Structure

When the IEEE committee sat down to sort out the range of numbers that were going to be used by all computers, they came out with 5 different ranges or, as we call them, "Classes" of IP Addresses and when someone applies for IP Addresses they are given a certain range within a specific "Class" depending on the size of their network.

To keep things as simple as possible, let's first have a look at the 5 different Classes:






In the above table, you can see the 5 Classes. Our first Class is A and our last is E. The first 3 classes ( A, B and C) are used to identify workstations, routers, switches and other devices whereas the last 2 Classes ( D and E) are reserved for special use.

As you would already know an IP Address consists of 32 Bits, which means it's 4 bytes long. The first octec (first 8 Bits or first byte) of an IP Address is enough for us to determine the Class to which it belongs. And, depending on the Class to which the IP Address belongs, we can determine which portion of the IP Address is the Network ID and which is the Node ID.

For example, if I told you that the first octec of an IP Address is "168" then, using the above table, you would notice that it falls within the 128-191 range, which makes it a Class B IP Address.

Understanding the Classes

We are now going to have a closer look at the 5 Classes. If you remember earlier I mentioned that companies are assigned different IP ranges within these classes, depending on the size of their network. For instance, if a company required 1000 IP Addresses it would probably be assigned a range that falls within a Class B network rather than a Class A or C.

The Class A IP Addresses were designed for large networks, Class B for medium size networks and Class C for smaller networks.

Ethernet Cables

Cat 1: Previously used for POTS telephone communications, ISDN and doorbell wiring.

Cat 2: Previously was frequently used on 4 Mbit/s token ring networks.

Cat 3: used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.

Cat 4: Defined up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.

Cat 5: Defined up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.Category 5 cable is a currently outdated standard that provides support for up to 100Mhz operation. It can be used for 10/100 Ethernet without worry, however for longer runs of 1000MbE it is recomended to use Cat. 5e or higher.

Cat 5e: Defined up to 100 MHz, and is frequently used for both 100 Mbit/s and 1000BASE-T Gigabit Ethernet networks. Category 5e cable provides support for frequencies up to 100Mhz. Cat. 5e generally provides the best price for performance, however for future proofing Cat. 6 or higher might be a better choice as it usually does not cost much more.

Cat 6: Defined up to 250 MHz, more than double category 5 and 5e. Category 6 is defined up to a frequency of 250Mhz. Allowing 10/100/1000 use with up to 100 meter cable length, along with 10GbE over shorter distances.

Cat 6a: Defined up to 500 MHz, double that of category 6. Suitable for 10GBase-T. It allows up to 10GbE with a length up to 100m.

Cat 7: Defined up to 600 MHz. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Category 7 is the informal name for "Class F" cabling defined by a different standards body than Cat. 6a and lower. It supports frequencies up to 600Mhz and may support the upcoming 100GbE standard.

Cat 7a: Category 7a is an upcoming standard that allows frequencies up to 1000Mhz. Supported Ethernet bandwidths have not been defined.