Basic TCP/IP configuration parameters

IP address

The IPv4 address identifies and differentiates your machine from all others on the network. It consists of a 32-bit binary number that is usually displayed as four octets expressed in decimal and separated by periods. An example IP address would be 172.16.2.2. You must have a unique IPv4 address for each machine on your IPv4-based network. In addition, if your machine serves as a router to another network, it contains two or more network adapters and belongs to two or more networks. In this case, you must assign each adapter a unique IPv4 address on the appropriate network.

NOTE: The IPv4 address differs from a MAC (Media Access Control) address in that it is configurable. A MAC address is a 6-byte address that is unique to each physical network adapter. This non-configurable address is assigned by the adapter manufacturer.

The IPv4 address consists of two parts: a network address that identifies the network and a host address that identifies the particular host, or node.

Several classes of TCP/IP networks are available, each based on the number of hosts a network needs. Use the smallest network class that can accommodate all of your network's hosts. Many TCP/IP installations use one or more Class C networks, but some larger installations might need to use Class B.

Internet address classes

Class Maximum number of
hosts per network Valid address ranges

A 16777214 1.0.0.1 through 9.255.255.254
11.0.0.1 through 126.255.255.254

B 65534 128.0.0.1 through 172.15.255.254
172.32.0.1 through 191.255.255.254

C 254 192.0.0.1 through 192.167.255.254
192.169.0.1 through 223.255.255.254

Private internets only 16777214
1048574
65534 10.0.0.1 through 10.255.255.254 (10/8)
172.16.0.1 through 172.31.255.254 (172.16/12)
192.168.0.1 through 192.168.255.254 (192.168/16)

Reserved - 0.0.0.0 through 0.255.255.255 (used if host will be assigned a valid address dynamically)
127.0.0.0 through 127.255.255.255 (loopback addresses)
224.0.0.0 through 239.255.255.255 (multicast addresses)
240.0.0.0 through 247.255.255.255 (future use)
248.0.0.0 through 255.255.255.254 (experimental)
255.255.255.255 (limited broadcast)

If you are connecting your machine to a pre-existing network, the network address (for Class A, the first octet; for Class B, the first two octets; and for Class C; the first three octets) is the same as those of other machines on the network. In this case, you need only concern yourself with creating a unique host address.

Class	Maximum number of hosts per network	Valid address ranges
A	16777214	1.0.0.1 through 9.255.255.254 11.0.0.1 through 126.255.255.254
B	65534	128.0.0.1 through 172.15.255.254 172.32.0.1 through 191.255.255.254
C	254	192.0.0.1 through 192.167.255.254 192.169.0.1 through 223.255.255.254
Private internets only	16777214 1048574 65534	10.0.0.1 through 10.255.255.254 (10/8) 172.16.0.1 through 172.31.255.254 (172.16/12) 192.168.0.1 through 192.168.255.254 (192.168/16)
Reserved	-	0.0.0.0 through 0.255.255.255 (used if host will be assigned a valid address dynamically) 127.0.0.0 through 127.255.255.255 (loopback addresses) 224.0.0.0 through 239.255.255.255 (multicast addresses) 240.0.0.0 through 247.255.255.255 (future use) 248.0.0.0 through 255.255.255.254 (experimental) 255.255.255.255 (limited broadcast)

If you are creating an entirely new network and you want to connect to the Internet, you must register its network address or addresses as described in ``Obtaining a domain name and an IP network number''.

If you do not want to connect to an outside network, you can choose any network address as long as it conforms to the syntax shown previously. In either case, once you determine the network address, you can then create the unique host address.

When you determine the IPv4 address, remember the following:

Each logical network must have its own network address.
All hosts in a network must have the same network address.
All hosts in a network must have unique host addresses.
The host portion of the address must not consist of all zeros or ones.
Do not use any of the addresses in the ranges shown as reserved in ``Internet address classes'', especially if your system can access the Internet