What Is a Dynamic IP Address?

A dynamic IP address is an IP address that's automatically assigned to each connection, or node, of a network, like your smartphone, computer, or tablet. This automatic assignment of IP addresses is accomplished by a DHCP server.

A DHCP-server-assigned IP address is called dynamic because it will often be different on future connections to the network.

Where Are Dynamic IP Addresses Used?

The public IP address that gets assigned to the router of most home and business users by their ISPs is a dynamic IP address. Larger companies usually don't connect to the internet using dynamic IP addresses and instead have static IP addresses assigned to them, and only them.

In a local network like in your home or place of business, where you use a private IP address, most devices are probably configured for DHCP, meaning they're using dynamic IP addresses. If DHCP isn't enabled, each device in your home network would need to have network information manually set up.

What Are the Advantages of Dynamic IP Addresses?

The main advantage of assigning IP addresses dynamically is that it's more flexible, and easier to set up and administer than static IP address assignments.

For example, one laptop that connects to the network can be assigned a particular IP address, and when it disconnects, that address is now free to be used by another device that connects later on, even if it's not that same laptop.

With this type of IP address assignment, there's little limit to the number of devices that can connect to a network, since ones that don't need to be connected can disconnect and free up the pool of available addresses for another device.

The alternative would be for the DHCP server to set aside a particular IP address for each device, just in case, that it wanted to connect to the network. In this scenario, a few hundred devices, no matter if they were being used or not, would each have their own IP address which could limit access for new devices.

Another advantage of using dynamic IP addresses is that it's easier to implement than static IP addresses. Nothing needs to be set up manually for new devices that connect to the network—all you have to do is make sure DHCP is enabled on the router.

Since almost every network device is configured by default to grab an IP address from the available pool of addresses, everything is automatic.

What Are the Disadvantages of Dynamic IP Addresses?

While it's extremely common, and technically acceptable, for a home network to use a dynamically assigned IP address for its router, a problem arises if you're trying to access that network from an outside network.

Let's say your home network is assigned a dynamic IP address by your ISP, but you need to remotely access your home computer from your work computer.

Since some remote access/desktop programs require that you know the IP address of your router to get to the computer inside that network (via port forwarding), but the IP address of your router changes periodically because it's dynamic, you could run into trouble.

A similar example could be given if you like to serve files from your home computer to remote users, like if you're running a website or your own file sharing server. Every time your IP address changes, any active downloads from your home server will abruptly stop, and your users will need to know your new IP address so they can reach your "new" server. This is a major reason most people don't set up such a service out of their house.

The reason behind these and similar issues can be summed up by the fact that a consistent IP address is necessary for establishing these kinds of connections. This is why users might opt for a dynamic DNS service. A DDNS service makes it easier to access your computer from outside your network because a specific name is assigned to your network, and that name is always tied to your current IP address, even if it changes.