PRB: DHCP Skips Addresses If Exclusion Range Included in Scope

• Microsoft Windows NT Server versions 3.5 and 3.51
• Microsoft Windows NT Server version 4.0

SYMPTOMS

When you use an exclusion range with DHCP, addresses offered to clients may not begin at the first address in the scope.

STATUS

This behavior is by design.

MORE INFORMATION

Leases offered to clients from a DHCP scope will be offered consecutively, starting with the first address in the IP address pool. But if an exclusion range is added to the scope, the first lease offered may not be the first address in the IP address pool.

For example, if a scope is created using a starting address of 165.224.113.11 and an ending address of 165.224.113.249, the first lease address offered to clients will be 165.224.113.11.

Alternatively, if an exclusion range of 165.224.113.100 to 165.224.113.120 is added to the scope, the first lease address offered will be 165.224.113.75. Leases will be offered consecutively through 165.224.113.249, skipping the excluded range. After 165.224.113.249, the next leases offered will be 165.224.113.11 through 165.224.113.74 consecutively.

This may also occur when multiple ranges of addresses are included in the DHCP scope.