TR-attached IPX SNA Client Not Find Server Across FDDI Bridge

• Microsoft SNA Server for Windows NT, versions 2.0, 2.1, 2.11, and 2.11.sp1

SYMPTOMS

When you run the SNA Server client software configured to use the Novell NetWare IPX/SPX client interface on Token Ring, the client is unable to find a SNA Server located across an FDDI transitional bridge.

When the problem occurs on a SNA Server Microsoft Windows 3.x client, Wnap.exe will display the following error when it is started:

   SNA Server Error: 546  Cannot establish connection with SNA Server
   <servername>.

CAUSE

When you connect a SNA Server IPX/SPX client from a Token Ring network to a SNA Server located on FDDI, the intervening FDDI bridge may bit-swap the destination address of the IPX/SPX connection request, causing the SNA client to fail to connect to the SNA Server.

This problem only occurs when SNA Server clients are configured to use NetWare IPX/SPX on Token Ring, where the server's IPX address is based on the network card adapter address installed in the SNA Server.

Ethernet-attached IPX clients will not encounter this problem because the FDDI bridge does not bit-flip destination addresses when bridging frames. Also, all other client-server connection methods supported by SNA Server (for example, named pipes, TCP/IP sockets, Banyan IP, and AppleTalk) do not directly refer to the server's adapter address when it connects to the server and will not encounter this problem.

RESOLUTION

To support this configuration, an update to the SNA Server client software is available that supports "bit flipping" of the SNA Server's IPX address. It will try if the following new SNA Server client setting is enabled:

   FlipMacAddress=Yes

For Windows NT clients, this settings must be set as follows:

  HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/SnaBase/
   Parameters/SnaSpx/

   FlipMacAddress: REG_SZ: Yes

   HKEY_LOCAL_MACHINE/Software/Microsoft/SnaBase/Parameters/SnaSpx/

   FlipMacAddress: REG_SZ: Yes

For additional information on the algorithm for bit-flipping network addresses, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q123791
   TITLE     : SNA Server Remote Station Discovery Process

STATUS

Microsoft has confirmed this to be a problem in SNA Server 2.0, 2.1, 2.11, and 2.11.sp1. This problem was corrected in the latest Microsoft SNA Server 2.11 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K