DHCP Server Delays Release of Client-Rejected IP Addresses

The information in this article applies to:

• Microsoft Windows NT Server versions 3.5 and 3.51

SUMMARY

If your computer running Windows NT Server and the Dynamic Host Configuration Protocol (DHCP) offers and reserves an IP address for a DHCP client, and the client takes a DHCP offer from another DHCP server, the DHCP server does not return the offered IP address to the pool of available addresses for 15 minutes.

MORE INFORMATION

The following events occur when a DHCP client requests an IP address when multiple DHCP servers are on the network:

1. When a DHCP client boots, it broadcasts a DHCPDISCOVER message to the network.

2. All DHCP servers in that network receive the DHCPDISCOVER message and they in turn send their DHCPOFFER messages via broadcast.

3. When a DHCP server sends a DHCPOFFER message, offering an IP address, the DHCP server reserves that IP address so that it cannot be offered to another DHCP client.

4. When the DHCP client accepts an IP address, the DHCP server that offered that address marks that address as being leased and the other DHCP servers return the offered IP addresses to the pool of available addresses, however, with a 15 minute delay. The address should be returned to the available pool of addresses as soon as the DHCP client requests an address from another DHPC server.

STATUS

Microsoft has confirmed this to be a problem in Windows NT versions 3.5 and 3.51. This problem was corrected in the latest U.S. Service Pack for Windows NT Workstation or Server version 3.51. For information on obtaining this update, query on the following word in the Microsoft Knowledge Base (without the spaces):

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