What is an IP?

Online database services use IPs to identify or authenticate users who access their products, rather than issuing passwords to users.  To do this, user IPs must be registered with the database service. When a user logs into the service the incoming IP is checked and verified for authorization, and access is either provided or denied as appropriate.

What does the term "IP" stand for?

IP refers to "Internet Protocol".  An IP address is the unique number assigned to each computer that resides on the Internet. 

The IP is a number and takes the form of:

xxx.xxx.xxx.* or xxx.xxx.xxx.xxx-xxx

x = a number

* = a range of numbers from 0-256

Host versus Network

There are two parts to every IP address, the network part and the host part.  Each IP address number is a decimal representation of an 8 bit binary number, therefore it can only range in decimal values from 0 -255.

The network IP uniquely identifies an organization. Depending upon the size of the organization, it may have one or more Class B or Class C addresses.

Class C address [ xxx.xxx.xxx.* ] represents up to 256 computers.
Class B
address [ xxx.xxx.* ] represents up to 256 times 256 (65,536) computers.

The remaining portion of an IP address is used to identify specific computers within an organization. This is sometimes referred to as a Class D address.

Class D address [ xxx.xxx.xxx.# ] represents a single computer.

Class D address [ xxx.xxx.xxx.3-3 ] represents several individual computers within a Class C network.

CIDR Notation

Classless Inter-Domain Routing (CIDR) is an expansion of the IP addressing system that allows for a more efficient and appropriate allocation of addresses.

CIDR changed fixed fields into variable-length fields, allowing addresses to be assigned with more granularity.

The CIDR IP address includes a number that tells how the address is split between networks and hosts.

For example, in the CIDR address the /20 indicates that the first 20 bits are used for network ID and the remaining 12 (there are 32 bits in the IP address) are used for host ID.