Microsoft KB Archive/133214

= DHCP Scope Exceptions =

Article ID: 133214

Article Last Modified on 2/20/2007

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APPLIES TO


 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Datacenter Server
 * Microsoft Windows 2000 Professional Edition
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition

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This article was previously published under Q133214



SYMPTOMS
Clients on your network may not be able to obtain leases from your Dynamic Host Configuration Protocol (DHCP) Server.



CAUSE
This behavior can occur if your scope is configured to lease the first and last addresses for a subnet.



RESOLUTION
To resolve this behavior, verify that the DHCP server's scopes are not leasing the first and last addresses of any defined scope that spans a whole subnet.



MORE INFORMATION
If you are using 100.25.1.0 as your network ID, and you are using a subnet mask of 255.255.255.0, the last octet would identify your hosts. As a result, both of the following IP addresses would be invalid: 100.25.1.0 and 100.25.1.255.

However, if the host ID portion of the address has a 255, or a 0, and it is in the middle of the scope, these addresses are valid.

For example, if you are using 100.25.0.0 as your scope, and the subnet mask is 255.255.0.0, the first address will be 100.25.0.0 and the last address would be 100.25.255.255. These are the only 2 illegal addresses in this range. An address of 100.25.1.255 would be valid and an address of 100.25.2.255 would also be valid.

The first and last address in a subnet are illegal and can cause irregular behavior in an environment if they were to be leased.

Additional query words: prodnt

Keywords: kbnetwork KB133214

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