A dynamic IP address is a temporary address for devices connected to a network that continually changes over time. An Internet Protocol (IP) address is a number used by computers to identify host and network interfaces, as well as different locations on a network.
Dynamic IP addresses are pulled from a pool of other IP addresses and change anywhere from within a few days to a few months. In contrast, static IP addresses assign a single, unchanging IP address to a home network.
When a dynamic IP address is necessary
Dynamic IP addresses are the most common type of IP address; they are the default IP address type provided by internet service providers (ISPs). In addition, dynamic IP addresses are ideal for everyday internet users because they are easy to manage and don't require users to go through any additional setup or network configuration. An organization or home network should nearly always use a dynamic IP address.
Static IP addresses -- which are IP addresses that don't change -- require extra setup and an additional fee. Dynamic IP addresses, however, don't have any additional costs connected to them. There's also a fixed limit to the number of static IP addresses because they are 32-bit numbers. Dynamic IP addresses mitigate this issue; new addresses are pulled from a pool of other changing IP addresses.
Dynamic IP addresses do not cost any extra and are simple to use. They can also be seen as more secure since they change often.
How does a dynamic IP address work?
When the internet was first conceived, the architects didn't foresee the need for an unlimited number of IP addresses. Consequently, there were not enough IP numbers to go around -- at least until the later advent of IPv6. To get around this problem, many ISPs limit the number of static IP addresses they allocate and economize on the remaining amount of IP addresses they possess by temporarily assigning an IP address to a requesting Dynamic Host Configuration Protocol (DHCP) computer from a pool of IP addresses. This temporary IP address is a dynamic IP address.
Requesting DHCP computers receive a dynamic IP address -- analogous to a temporary phone number -- for the duration of that internet session or for some other specified amount of time. Once users disconnect from the internet, their dynamic IP address goes back into the IP address pool so it can be assigned to another user. Even if users reconnect immediately, it is unlikely they will be assigned the same IP address from the pool.
When a user registers with a domain name system (DNS) service and connects to the internet with a dynamic IP address, the user's computer contacts the DNS service and lets him know what IP address it has been assigned from the pool. The service then works with the DNS server to forward the correct address to the requesting DHCP computer. Using a dynamic DNS service to arrange for computers to find a user, even though they are using a dynamic IP address, is the next best thing to having a static IP.
Pros and cons of dynamic IP addresses
Dynamic IP addresses host benefits such as the following:
- They don't require maintenance, making it ideal for home use, where users might not have a lot of technical knowledge.
- Network configuration is done automatically, meaning that users don't have to worry about configuring their IP address.
- Dynamic IPs are more economical, considering there are a limited number of static IPs.
- Dynamic IPs are more cost-effective compared to static IPs.
- They present lower security risks, since a device is assigned a new IP address each time a user logs on.
Although dynamic IP addresses are commonly used, they still have some disadvantages that users should be aware of, including the following:
- There is the possibility of network failure, which has the potential to cause extended downtimes -- for example, if a DHCP server fails.
- There could be security issues around DHCP automation -- for example, if control over a DHCP server is lost, then users who connect to it could be intercepted, and their information could be stolen.
- Dynamic IPs are less reliable for tasks such as voice over IP (VoIP), a virtual private network (VPN) or playing games online, as the service could disconnect.
- Geolocation services will have a harder time finding the accurate location of a device.
- Businesses with dynamic IP addresses may prefer employees to work on-site to ensure secure access to their network's servers.
- Dynamic addresses need a program to assign and change IP addresses.
Static vs. dynamic IP addresses: Key differences
The main difference between static and dynamic IP addresses is in the terminology of static and dynamic. In a literary sense, the term static character means a character that stays the same throughout a story, and the term dynamic character refers to a character that changes throughout a story. Static and dynamic IP addresses follow the same pattern -- static refers to unchanging, and dynamic refers to changing. This means that the numbers associated with a static IP address do not change, while the numbers associated with a dynamic IP address do change.
Normally, a dynamic IP address can stay the same for days, weeks or longer but can also be changed by the ISP or through a reset of the router or modem. The address change does not affect the end user either -- the address can even change while the user is on the web. In most cases -- such as in-home use -- when an ISP assigns a device an IP address, it will be a dynamic IP address.
A static IP address does not change and, in most cases, will cost an additional fee through the ISP. Static IP addresses must be reserved from a limited number of IP addresses. Static IP addresses will stay the same no matter what users do, unless they request their ISP to change them. Businesses might want to use a static IP address to ease operations.
In most cases, a dynamic IP address is the cheaper, better option.
On a base level, dynamic IP addresses generally have better security compared to static IP addresses because they change with each session or login. This makes it more difficult for a hacker to track and compromise an individual's data. A hacker will have a harder time targeting networked equipment on a dynamic IP address.
Dynamic IP addresses may be more secure, but they still come with some security concerns. Namely, there are security issues around DHCP automation. If the control over a DHCP server is lost, then users who connect to it could be intercepted, and their information could be accessed. Businesses with dynamic IP addresses may prefer employees to work on-site to ensure secure access to their network's servers. Employees might also have a harder time connecting to a dynamic IP address from remote access controls, which may discourage them from working off-site.
However, security deficiencies found in dynamic IP addresses can be mitigated by implementing a router firewall, security suite or VPN. A VPN, for example, can help in obscuring a user's network address, making it more difficult to find a device's physical location. Although these measures don't guarantee that all data will be safe at all times, they can help by a large margin, making it a good idea to implement additive security processes.