Internet Router Discovery Protocol (IRDP) Client Support Added to Windows NT 4.0

ID: Q223756

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

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

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.

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: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

Router discovery is configured from the following registry keys:

Start Registry Editor (Regedt32.exe).

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.

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.

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/

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://www.microsoft.com/support/supportnet/overview/overview.asp

STATUS

Microsoft has confirmed this to be 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

Additional query words: 4.00

Keywords : kbnetwork ntsp kbbug4.00 kbfix4.00 nt4sp5fix
Version : winnt:4.0
Platform : winnt
Issue type : kbbug