DOCUMENT:Q169122 25-FEB-2002 [winnt] TITLE :Non-rfc Compliant DHCP Server Does Not Send DHCPNAK to Client PRODUCT :Microsoft Windows NT PROD/VER::4.0 OPER/SYS: KEYWORDS:kb3rdparty kbnetwork ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server version 4.0 ------------------------------------------------------------------------------- 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 ====================================================================== Keywords : kb3rdparty kbnetwork Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 Version : :4.0 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.