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Q169122: Non-rfc Compliant DHCP Server Does Not Send DHCPNAK to Client

Article: Q169122
Product(s): Microsoft Windows NT
Version(s): 4.0
Operating System(s): 
Keyword(s): kb3rdparty kbnetwork
Last Modified: 25-FEB-2002

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The information in this article applies to:

- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server version 4.0 
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SUMMARY
=======

When a Windows NT DHCP client is moved to another subnet (without issuing the
ipconfig/release command before moving), the client will request its previous IP
address. Usually this IP address is not valid for usage on the new subnet.

When a DHCP server detects that the client requests an IP address that does not
fit for the current subnet, the DHCP server must send a DHCPNAK to the client
(according to RFC1541).

Some non-rfc compliant DHCP servers do not send this DHCPNAK. Because of this,
the client does not attempt to lease a new IP address on the new subnet and
tries to use its old IP address (see the frame information later in this
article).

This problem has been experienced only when using a third-party DHCP server. The
Microsoft Windows NT DHCP server does not experience this behavior.

MORE INFORMATION
================

Per RFC1541, a DHCP server sends a DHCPNAK to a client that requests an IP
address but is not located on the current subnet. According to RFC1541 (page
28):

  In particular, if the previously allocated network address in the ciaddr
  field from the client does not match the network address recorded by the
  server for that client, the server sends a DHCPNAK to the client.

After receiving a DHCPNAK, the DHCP client will restart the DHCP lease process by
sending DHCPDISCOVER.


RESOLUTION
==========

Contact the non-rfc compliant DHCP server vendor for assistance or use the
Microsoft Windows NT DHCP server.

Additional query words: SRD970304000093

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Keywords          : kb3rdparty kbnetwork 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : :4.0

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