3.2. The IP address

3.2.1.Static versus dynamic IP addressing
3.2.2.Routable versus non-routable IP addresses

An IP address is an identifying number assigned to all devices connected to the Internet, and is used in routing information from one device to another. Like your phone number, your IP address enables other people to reach you. In our standard configuration, your ISP only needs to allocate one IP address for your network. It is assigned to your server, which will accept all the Internet data packets intended for your network and distribute them to the appropriate computer - much like an office receptionist is able to accept incoming calls and direct them to the appropriate extension.

3.2.1. Static versus dynamic IP addressing

A static IP address never changes. It is permanently assigned to your server by your ISP.

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Static IP addressing is preferable to dynamic IP addressing because it makes it easier for users on the Internet to connect to your services.

Dynamic IP address assignment means that your IP address is assigned to you only temporarily and may be changed by your ISP. This makes it more difficult to ensure continuity of service to your network. Consider again our telephone number analogy. When your telephone number changes, you are able to place outgoing calls. However, until your new phone number is registered with Directory Services, other people are unable to look up your new number and place calls to you. Similarly, whenever your IP address changes, a record associating your server with its new IP address must be published with the equivalent of Directory Services (known as Domain Name Service or DNS) before incoming traffic can find you.

If your IP address is dynamically assigned and you have a dedicated connection to your ISP (for example, with a typical cablemodem), you may find it helpful to use a dynamic DNS service . We strongly recommend you review Appendix B: Dynamic DNS services for more information about this worthwhile option.

3.2.2. Routable versus non-routable IP addresses

If an IP address is analogous to your phone number, then a routable IP address is the equivalent of a full telephone number complete with country code and area code such as +1-613-555-1234. Using the same analogy, a non-routable address is the equivalent of an office extension. If your server is assigned a non-routable address, it cannot directly receive incoming Internet connections, which limits the services that it can provide to your site.