Event ID 1020 — DHCP Lease Availability

Updated: January 8, 2009

Applies To: Windows Server 2008 R2

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Internet Protocol (IP) addresses are leased by the Dynamic Host Configuration Protocol (DHCP) server to its clients. Each lease has an expiration date, which the client must renew if it is going to continue to use that IP address. The DHCP server cannot issue leases to clients if the number of available IP addresses in the scope is insufficient.

Event Details

Product: Windows Operating System
ID: 1020
Source: Microsoft-Windows-DHCP-Server
Version: 6.1
Symbolic Name: EVENT_SERVER_LOW_ADDRESS_WARNING
Message: Scope, %1, is %2 percent full with only %3 IP addresses remaining.

Resolve

Extend DHCP scopes, reduce lease times, or decrease cleanup interval

If the DHCP server does not have IP addresses available to provide to the requesting client, then the request fails, and the client might not be able to communicate with other computers on the network. When this occurs, consider the following possible solutions:

  • Use scope extension to expand the address range for the current scope.
  • Reduce the lease duration and decrease the cleanup interval. This can help to speed the reclaiming of expired scope IP addresses.

Extend the DHCP scopes

If you already have a DHCP scope and the Start Address and End Address do not currently include all addresses for your specific subnet, you can increase the number of addresses in the scope by extending the Start Address or End Address in the scope properties.

To perform these procedures, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.

To increase the number of addresses available to clients:

  1. At the DHCP server, click Start, point to Administrative Tools, and then click DHCP.
  2. In the console tree, right-click the scope you want to extend, and then click Properties.
  3. Change Start IP Address and End IP Address to extend the scope.

Reduce the lease duration

To perform these procedures, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.

To reduce the lease duration:

  1. At the DHCP server, click Start, point to Administrative Tools, and then click DHCP.
  2. In the DCHP console tree, right-click the scope you want to configure, and then click Properties.
  3. On the General tab, under Lease duration for DHCP clients, type the new lease duration.

Decrease the cleanup interval

To perform these procedures, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.

To use a Netsh command to set the cleanup interval time:

  1. At the DHCP server, click Start, click Run, type cmd, and then press ENTER.
  2. Type netsh dhcp set databasecleanupinterval "NewInterval" (where "NewInterval" is the amount of time in minutes between DHCP database cleanups).

Example

In the following example, this command sets the database cleanup interval to 10,080 minutes (every seven days).

netsh dhcp set databasecleanupinterval 10080

Verify

To verify that the DHCP server has enough IP addresses available to lease, ensure that Scope in the DHCP console tree displays a green up arrow icon.

To perform these procedures, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.

  1. At the DHCP server, click Start, point to Administrative Tools, and then click DHCP.
  2. In the DHCP console tree, view the scope icon. It should be a green up arrow.

Related Management Information

DHCP Lease Availability

DHCP Infrastructure

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