IP address is short for Internet Protocol (IP) address. An IP addressis an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. Contrast with IP, which specifies the format of packets also called datagrams, and the addressing scheme.
An IP is a 32-bit number comprised of a host number and a network prefix, both of which are used to uniquely identify each node within a network.To make these addresses more readable, they are broken up into 4 bytes, or octets, where any 2 bytes are separated by a period. This is commonly referred to as dotted decimal notation.The first part of an Internet address identifies the network on which the host resides, while the second part identifies the particular host on the given network. This creates the two-level addressing hierarchy.All hosts on a given network share the same network prefix but must have a unique host number. Similarly, any two hosts on different networks must have different network prefixes but may have the same host number. Subnet masks are 32 bits long and are typically represented in dotted-decimal (such as 255.255.255.0) or the number of networking bits (such as /24).
|
Class
|
Address
Range
|
Default
Subnet Mask
|
Number
Of Networks
|
Host
per Network
|
|
Class
A*
|
1.0.0.1
to 126.255.255.254
|
255.0.0.0
|
126 (27 –
2)
|
16,777,214 (224 –
2)
|
|
Class
B
|
128.1.0.1
to 191.255.255.254
|
255.255.0.0
|
16,382 (214 –
2)
|
65,534 (216 –
2)
|
|
Class
C
|
192.0.1.1
to 223.255.254.254
|
255.255.255.0
|
2,097,150 (221 –
2)
|
254 (28 –
2)
|
|
Class
D
|
224.0.0.0
to 239.255.255.255
|
Reserved for Multicasting
|
||
|
Class
E
|
240.0.0.0
to 254.255.255.254
|
Experimental, used for Research
|
||
*Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.
The host's formula will tell you how many hosts will be allowed on a network that has a certain subnet mask. The host's formula is 2n - 2. The "n" in the host's formula represents the number of 0s in the subnet mask, if the subnet mask were converted to binary.
A subnet mask is what tells the computer what part of the IP address is the network and what part is for the host computers on that network. Subnetting is the process of breaking a large network into smaller networks by adding 1s to the subnet mask.Today, classless IP addresses are used almost exclusively, and classful IP addresses are used only for certification testing or older routing protocols.A default gateway is where a device sends packets that are destined for a device not on the local LAN. Again, the device knows what is and what is not on the local LAN by the subnet mask.Private IP addresses are used by most networks today, and these special, non-routable IP addresses are translated to public Internet IP addresses when those devices need to talk to the Internet.
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