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Q223756: IRDP Client Support Added to Windows NT 4.0

Article: Q223756
Product(s): Microsoft Windows NT
Version(s): 4.0
Operating System(s): 
Keyword(s): kbnetwork kbWinNT400sp5fix
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Server, Enterprise Edition version 4.0 
- Microsoft Windows NT Workstation version 4.0 
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IMPORTANT: This article contains information about modifying the registry. Before you 
modify the registry, make sure to back it up and make sure that you understand how to restore 
the registry if a problem occurs. For information about how to back up, restore, and edit the 
registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

You require Internet Control Message Protocol (ICMP) Internet Router Discovery
Protocol (IRDP) support on Microsoft Windows NT

CAUSE
=====

IRDP (router discovery) support has been added to Windows NT 4.0. IRDP support
has also added to Windows 95 and 98 (see the "More Information" section of this
article).

The following text is an excerpt from Request for Comments (RFC) 1256:

  The ICMP router discovery messages are called "Router Advertisements" and
  "Router Solicitations. " Each router periodically multicasts a Router
  Advertisement from each of its multicast interfaces, announcing the IP
  address(es) of that interface. Hosts discover the addresses of their
  neighboring routers simply by listening for advertisements.

This is one way of testing for dead gateways. This solution requires that routers
be configured to send IRDP router advertisement packets.

RESOLUTION
==========

Windows NT 4.0 now supports performing "router discovery" as specified in RFC
1256.

Router discovery provides an improved method of configuring and detecting default
gateways. When using DHCP or manual default gateway configuration, there is no
way to adjust to network changes. Using router discovery, clients dynamically
discover routers and can switch to backup routers if a network failure or
administrative change is needed. Router discovery is made up of two types of
packets: Router Solicitations sent by hosts, and Router Advertisements sent by
routers. Windows NT 4.0 supports router discovery as a host only.

This feature is disabled by default.

Client Configuration
--------------------

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

Router discovery is configured from the following registry keys:

1. Start Registry Editor (Regedt32.exe).

2. Locate the following key in the registry:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<adaptername>\Parameters\Tcpip\

  Value Name: PerformRouterDiscovery
  Value Type: REG_DWORD - Number
  Valid Range: 0,1
  Default: 0
  Description: This parameter controls whether Windows NT will attempt to
  perform router discovery per RFC 1256 on a per-interface basis. This
  parameter defaults to 0 or FALSE.

3. Locate the following key in the registry:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<adaptername>\Parameters\Tcpip\

  Value Name:SolicitationAddressBcast
  Value Type: REG_DWORD - Number
  Valid Range: 0,1
  Default: 0
  Description: This parameter can be used to configure Windows NT to send router
  discovery messages as limited broadcasts (255.255.255.255) instead of
  multicasts, as described in RFC 1256. By default, router discovery
  solicitations are sent to the all routers multicast group (224.0.0.2).
  By default, IRDP client listens to both multicast and broadcast router
  advertisements.

4. Quit Registry Editor.

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the
individual software update. For information on obtaining the latest service
pack, please go to:

- http://www.microsoft.com/Windows/ServicePacks/

-or-

- Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For information on obtaining the individual software update, contact Microsoft
Product Support Services. For a complete list of Microsoft Product Support
Services phone numbers and information on support costs, please go to the
following address on the World Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS


STATUS
======

Microsoft has confirmed that this is a problem in Windows NT 4.0. This problem
was first corrected in Windows NT version 4.0 Service Pack 5.

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

When a host that supports router discovery initializes, it joins the
"all-systems" IP multicast group (224.0.0.1), and then listens for the router
advertisements sent to that group.

Router Solicitation
-------------------

Hosts send ICMP Router Solicitation messages to the all routers IP multicast
address (224.0.0.2). The router will respond by sending a router advertisement.
This ensures the client receives a default gateway immediately without waiting
for a periodic router advertisement. Windows NT sends a maximum of 3
solicitations at intervals of approximately 600 milliseconds.

NOTE: If multiple default gateways (0.0.0.0 routes) have a metric of 1, random
routing behavior can occur. For additional information, please see the following
article(s) in the Microsoft Knowledge Base:

  Q159168 Multiple Default Gateways Can Cause Connectivity Problems

For IRDP support, Windows 95 requires Windows Socket update 2; Windows 98
natively supports IRDP. For additional information, please see the following
article(s) in the Microsoft Knowledge Base:

  Q183902 Dead Gateway Detection Is Not Triggered During Logon

For additional information about the IPRIP Listener Tool for Windows 98, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q194464 Description of the Microsoft IPRIP Listener Tool for Windows 98

Additional query words: 4.00

======================================================================
Keywords          : kbnetwork kbWinNT400sp5fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400
Version           : :4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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