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Q164394: BOOTP Service Does Not Populate ARP Cache

Article: Q164394
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 09-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
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SYMPTOMS
========

Windows NT 4.0 Service Pack 2 (SP2) provides a new feature that allows the DHCP
Service to respond to BOOTP requests as well as DHCP requests.

From RFC 1048, the BOOTP service is defined as follows:

  "The Bootstrap Protocol (BOOTP) is a UDP/IP-based protocol that allows a
  booting host to configure itself dynamically, and more significantly, without
  user supervision. It provides a means to assign a host its IP address, a file
  from which to download a boot program from some server, that server's
  address, and (if present) the address of an Internet gateway."

This means that a BOOTP server should provide 2 basic functions:

1. Provide IP addresses to hosts who request them, without user intervention.
  Additionally, the host should be provided with other relevant information,
  such as default gateway address, name server address, and so forth.

2. Provide location of image for client to start from. This is most often a
  diskless workstation.

For BOOTP clients that only require an IP address from the Windows NT BOOTP
server, their clients simply request an address and the Windows NT Server
provides the IP address.

In the case where the host starts from an image file on a server, this is similar
to how Remote Program Load (RPL) is used for remoteboot in a Microsoft
networking environment.

Typical BOOTP session:

1. Client sends BOOTP request

2. Server sends response containing:

   - client's IP address

   - boot image filename

   - boot image servername

   - other common IP parameters (router, dns, etc)

3. Client starts trivial file transfer protocol (TFTP) download of boot image
  file from boot image server.

In this scenario, when the boot image server is specified as the Windows NT
DHCP/BOOTP server, the client is never able to download the boot image.

CAUSE
=====

There are two issues with using Windows NT as a BOOTP server, where an Image
file is required:

1. The download of the image file is done using TFTP. Windows NT does not
  include a TFTP server service. To use Windows NT DHCP/BOOTP Server with BOOTP
  clients who must boot from an image file (usually diskless workstations), a
  third-party TFTP server is required. For more information on TFTP, see the
  following article in the Microsoft Knowledge Base:

  ARTICLE-ID: Q142373
  TITLE : TFTP Server Not Included With Windows NT

2. There is a bug in the BOOTP function of the DHCP Service. When the BOOTP
  client tries to start the TFTP session with the server, the server does an
  address resolution protocol (ARP) query for the client's media access control
  address. The client does not have a full operating system or TCP/IP stack
  loaded at this time because it is dependent on the boot image file, therefore
  the client never responds to the ARP request. The BOOTP service on the
  Windows NT DHCP/BOOTP server should have populated the ARP cache with the
  client address information when it sent the BOOTP response.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 4.0 Service
Pack 2. We are researching this problem and will post new information here in
the Microsoft Knowledge Base as it becomes available.

Additional query words: bootp arp tftp
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Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : WinNT:4.0
Issue type        : kbbug

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