Network Load Balancing servers are removed from the Internet Group Management Protocol membership list in Windows Server 2003 (838408)

CAUSE

This problem occurs because Network Load Balancing IGMP report messages are not synchronized with host membership queries from the router or from the switch. The IGMP stack that is used by the Network Load Balancing client is hard-coded to send a report message every 60 seconds. IEEE RFC 1112 specifies that the client software must respond to IGMP membership queries after a randomly selected delay that is not greater than 10 seconds. However, the Network Load Balancing report messages are not synchronized with the IGMP membership queries in Windows Server 2003. This scenario causes the router or the switch to drop the Network Load Balancing client from the membership list.

RESOLUTION

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.micr osoft.com/default.aspx?scid=fh;[LN];CNTACTMS

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

No prerequisites are required.

Restart requirement

You do not have to restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Windows Server 2003, 64-Bit Edition

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   06-May-2004  16:50  5.2.3790.170      381,952  Wlbs.sys

Windows Server 2003, 32-bit editions

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   06-May-2004  20:00  5.2.3790.170      169,984  Wlbs.sys

WORKAROUND

To work around this problem, do not use IGMP. To avoid using IGMP, configure Virtual Local Area Networks (VLANs) to isolate Network Load Balancing traffic to a subset of ports on the switch. If you use this workaround, you must reconfigure both the switch and the Network Load Balancing nodes from IGMP multicast mode to unicast mode.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

193602 Configuration options for WLBS hosts connected to layer 2 switches