Computers & ProgrammingComputers & NetworkingWindows Server

DHCP Reservation Limitations in Windows 2008 R2

With Windows Server 2008 R2, you may encounter that you are unable to add a DHCP reservation if the reservation you are attempting to create is not within the address pool range. For Example:

Scope 192.168.1.0
Address Pool 192.168.1.1192.168.1.100
Subnet Mask 255.255.255.0

Reservation: 192.168.1.101

Consider the following scenario:

  1. You have a computer that is running Windows Server 2008 R2.
  2. Dynamic Host Configuration Protocol (DHCP) Server role is installed.
  3. There is an active scope on the DHCP server
  4. The distribution range does not cover all IP addresses in the scope.
  5. You try to add a reservation to the scope, but the reservation is outside the scope range.

The reservation for 192.168.1.101 may fail. The error message that will be displayed is: “The specified DHCP client is not a reserved client”

The Windows 2008 R2 DHCP Server won’t allow reservations to fall outside of the configured address pool. To resolve this issue, expand the address pool to cover the entire subnet.

If you do not want the DHCP server to assign addresses in a portion of the address pool, create an exclusion range. DHCP Reservations can be created even if they fall within an exclusion range.

The new scope for this example should look like this:

Scope 192.168.1.0
Address Pool 192.168.1.1192.168.1.254
Exclusion Range 192.168.101192.168.1.254
Subnet Mask 255.255.255.0

Reservation: 192.168.1.101

Alternatively, you could install a hotfix, that is available on the Microsoft website, to correct this behavior.

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