What is DHCP Lease Time & What Should I Set it To?

If you've ever set up a router at your home or business, one of the settings you may have noticed is DHCP lease time. Unless you're an experience IT professional, it's highly likely that you may have bypassed this setting completely, especially if you aren't sure what it does or what value you should assign to this field.

If multiple devices are going to be connected to your internet service, it's crucial that you understand what this term means, as well as what settings are best for your personal or business needs.

What Exactly Is DHCP Lease Time?

You may already be familiar with a home lease. A home lease is when a tenant signs a contract and is permitted to live in the home for the time outlined in the contract. Once that time has expired, a different tenant will most likely move into the home. Much like a lease for a house or apartment, a DHCP lease time works in the same way.

DHCP stands for Dynamic Host Control Protocol. This server is responsible for "leases" of IP addresses. Every device that is connected to a network must have an IP address, from the laptops in your home to the desktop computers in your office to smartphones, smart TVs, tablets, and other connected devices.

The IP address is similar to a home's address. In order to receive mail, a home must have an address. In order to send and receive data, a device must have an IP address that identifies it when it is connected to the internet. Networks have two IP addresses - the first and last of a series. The numbers that fall in between are reserved for use for other devices to be used on the network.

While some devices may have a permanent IP address, others will just have temporary IP addresses, which is where the DHCP lease time - also known as client lease time - comes into play. Temporary IP addresses are assigned to other devices that don't require a set IP - a visitor using a company's free Wi-Fi, for example. After a set period of time, if the device is not connected to the LAN server, the IP address expires for the device and is reassigned to another device. This set period of time is the DHCP lease time.

Sound complicated? It's not as complicated as it may seem. Take a coffee shop for example. This coffee shop advertises free Wi-Fi for its patrons. Since the average patron will not be hanging around the coffee shop all day, every day, their device (laptop, tablet, or smartphone, for example) will not require its own permanent IP address. Instead, it will be assigned an IP with a DHCP lease time.

Once the lease time expires, the IP will be assigned to another device - such as the smartphone of a new customer. This way, multiple people can connect to the network without any problems and without all of the IP addresses being taken.

When to Adjust Your DHCP Lease Time

If you run a business or work in an office where multiple devices are in use, you'll want to consider adjusting your DHCP lease time, particularly if you have employees, customers, or clients who use their devices occasionally. Failure to adjust the lease time will likely result in a shortage of IP addresses. You want to make sure that any IP addresses that are being used just temporarily expire after a set amount of time.

You may even have to set the DHCP lease time on your home network if you have many devices. In this case, a longer lease time may be sufficient for devices that are used fairly frequently but not daily, like your router.

Finding the Optimum DHCP Lease Time for Your Needs

There is no set rule of thumb for the settings for your DHCP lease time, and it may require some experimentation based on your own personal needs (or those of your business) to get the timing just right.

Typically, the DHCP lease time default setting on most servers is 24 hours. However, this may be shorter or longer depending on your own server. Settings can be adjusted from one minute up to a certain number of days.

You'll want to avoid setting the lease time too low as this can cause interruptions to service. For example, even in a busy doctor's office, coffee shop, or other business that offers wireless service to its customers and clients, a person may spend much longer than one minute browsing the internet on their phones. Setting the lease time for just a few minutes will result in interruptions and aggravation. If connected device settings have a fairly quick turnaround, the settings may need to be lower than 24 hours.

In your household, if you use devices on a fairly frequent basis and don't have many additional devices connected, the lease time can be set to several weeks or even months. The lower the number the connected devices, the higher the setting can be. The more devices that are connected, the lower the setting should be.

In an office where users go online on their computers to work, setting a static IP for each workstation is advised. However, for other device usage, keeping several IP addresses open and finding the proper lease time is necessary. Again, this should be based on turnaround times of different devices that are connected, and the number can be adjusted accordingly.

Who Sets the DHCP Lease Time?

This task is frequently performed by the system administrator. The administrator should be made aware of your particular needs to set the lease time accordingly. Of course, it is entirely possible that you may find that some adjustments are needed, or your needs may change down the road. You want to ensure that your settings are sufficient for the number of devices connected and that your server isn't completely overloaded.

Final Thoughts

Setting the DHCP lease time for your server is critical to performance. Whether you want to keep your employees connected or you want to keep your customers happy by providing wireless, you have to make sure that this setting is adjusted to keep the server open for new connections.

When setting the lease time, it's important to remember the following:

  • High turnaround for devices need a shorter lease time. Often, 24 hours is sufficient, but this may need to be adjusted if it's just not working for you.
  • When fewer devices will be connected, DHCP lease times can be longer.
  • Devices that are permanently in use should have their own static IP addresses.
  • Devices that are used frequently but don't necessarily require a static IP can have a longer lease time - think days, weeks, or even months.
  • Default times vary by server. While most are set to 24 hours, this isn't true for every server.
  • Never set the lease time so low that it can lead to interruptions and frustration. Are you struggling to find your correct setting? Are you unsure of how to proceed? Leave your comment below to find out more about changing your DHCP lease times.

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