Static and Dynamic IP Addresses
An IP address is a series of numbers separated by dots that act like an address or telephone number for a computer connected to the Internet. IP addresses look like this: 323.457.965.82. When computers need to exchange information, they use each other's IP addresses to find each other.
Static IP Addresses
A static IP address never changes. A computer with static IP address always identifies itself by this one permanent IP address.
When you access the internet and you want to visit www.spamlaws.com, you type this web address into your browser. Your computer takes this web address and asks a domain name system (DNS) server for the corresponding IP address for www.spamlaws.com (in this way the DNS server acts like a phone directory). Your computer then uses this address to connect to the server for the website www.spamlaws.com.
With a permanent IP address, the number identifier will never change. It is like a permanent home phone number.
Dynamic IP Addresses
Because there are only a limited number of IP addresses, it is not possible for every computer that connects to the Internet to have its own permanent IP address - there are simply not enough to go around. However, this problem can be avoided by using dynamic IP addresses.
When you have a Dynamic Host Configuration Protocol (DHCP) configured computer, you are using dynamic IP addresses. This means instead of your computer having one static, permanent IP address, it gets a new IP address each time it connects to the Internet. When your DHCP computer connects to the Internet, it requests a temporary IP address from your Internet service provider (ISP). They then assign your computer a dynamic IP address from the pool of temporary IP addresses they use for this purpose. For the duration of your Internet session your computer is identified by this IP address and then when you disconnect from the Internet the address goes back into the pool to be used by someone else. Your chances of getting the same dynamic IP address back again are low.
Using a dynamic IP addresses is like using a payphone - you can call out and it doesn't really matter what number the call is coming from. However, this can be a nuisance if you want other computers to be able to find and identify your computer (for example if you are using a VoIP application) since it does not have a permanent IP address.
To solve this problem you would need to request a static IP address from your ISP or use a dynamic DNS service. Both will involve an additional monthly fee.
Dynamic DNS Services
You can request a dynamic DNS service for your ISP for an additional monthly fee. When your DHCP computer connects to the Internet and requests a dynamic IP, it also informs the DNS service what IP it has been assigned from the pool. The DNS service will then give this number to any computers requesting your IP address. Think of it as a call forwarding system.
Every time you log into the Internet and get a new dynamic IP address, your computer updates the DNS service with its new number, and other computers will continue to be able to find yours.