What is DHCP Lease Time?

Computers that are set up to automatically retrieve IP addresses from a DHCP (Dynamic Host Configuration Protocol) server are given an IP address that is only valid for a certain amount of time. The DHCP Lease Time is the name given to this period of time. This IP address becomes available when the lease expires and can be assigned to another device on the network.

The client tries to extend the lease of the specified IP address on the DHCP server after half (1/2) of the lease term has passed. The client does this by sending a DHCPREQUEST request to the server. The DHCP server sends a DHCPACK message with the new lease time and TCP/IP setup information if the IP address lease can be extended. The DHCP client adjusts its network settings after getting confirmation. If the DHCP client fails to renew the IP address lease, it will attempt again.

The client will send a broadcast DHCPREQUEST packet to communicate with any accessible DHCP server in the network when 87.5 percent (7/8) of the lease time has expired.

ipconfig /all

You will see the date of obtaining an IP address, and the expiration time:

Lease Obtained. . . . . . . . . . : Friday, July 5, 2019 4:57:31 PM
Lease Expires . . . . . . . . . . : Saturday, July 13, 2019 4:57:31 PM

How to Change DHCP Lease Time in Windows Server?

The DHCP server on Windows Server employs an 8-day lease time by default. In most circumstances, this is the best option. If your IP subnet has a lot of free addresses, you can reduce the Lease Time setting to get unused IP addresses released sooner.

Optimal values DHCP lease time for different network types:

  • For wired Ethernet networks – 8 days;
  • For wireless networks – 1 day;
  • For guest Wi-Fi networks – 2-8 hours;

You can change lease time settings for each scope on the DHCP server. In this example, we will show how to reduce DHCP Lease Time from 8 to 2 days on Windows Server 2012 R2.

  1. Run the DHCP management console—dhcpmgmt.msc;
  2. Open the properties of the DHCP scope for which you want to reduce the lease time;
  3. On the “General” tab in the “Lease Duration for DHCP clients” section, in the “Limited to” field, specify a new lease time for clients of this scope (you can even completely disable the lease time, in this case, the IP addresses will be issued to devices permanently);
  1. Save your changes by clicking OK.

New DHCP lease time settings will apply for DHCP requests from new clients of the DHCP server and on the next renewal of the IP address by old clients.

You can also change the DHCP Lease time for a specific scope using the Set-DHCPServerv4Scope PowerShell cmdlet:

Set-DHCPServerv4Scope ScopeID -LeaseDuration 2.00:00:00

With the Acquire-DHCPServerv4Scope command, you may get the current properties after updating the DHCP scope parameters.

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