Connecting over TCP/IP to SNA Server with Multiple Net Cards

ID: Q128986

The information in this article applies to:

• Microsoft SNA Server for Windows NT, version 2.1

SYMPTOMS

When connecting from an SNA Server client using the TCP/IP sockets interface to SNA Server, the following problems may occur if the Windows NT TCP/IP Protocol is bound to more than one network card on the server, and different IP addresses are configured for each card:

• When opening a 3270 session, the session may never activate (the SNA 3270 applet may display "No SNA Server found in domain" on the status line).
• When opening a 5250 session, an APPC error may occur (F004 - or AP_COMM_SUBSYSTEM_NOT_LOADED). This indicates that the SNA client could not locate a running SNA Server in the domain which supports the local and remote LU aliases being requested.
• If multiple SNA Servers are configured the same way, the client may not be able to open a session through one or more of the servers, but not all.

CAUSE

When SNA Server is configured (using SNA Setup) to accept client sessions over TCP/IP sockets, SNA Server only searches for the first IP address that is configured on the server. The first IP address corresponds with the first adapter that the Windows NT TCP/IP Protocol is bound to.

When an SNA client opens its "sponsor connection" to an SNA Server in the domain, SNA Server sends down the server name and IP address it finds. However, the SNA client may not be able to connect to the server over this first IP address since the IP address may only be available over the other server's network card.

RESOLUTION

• Configure the TCP/IP protocol on the Windows NT Server using the Control Panel / Network option and select the Enable IP Routing option. This will cause the client to be able to connect to either IP address supported by the server

  -or-

• Control which IP address is used by the SNA Server clients by configuring the Windows NT TCP/IP Protocol on SNA Server to bind to the desired adapter:

  1. Open the Network icon in Control Panel

  2. Choose the Bindings button

  3. Select the TCP/IP Protocol and choose OK

  4. Select the desired adapter and choose the "up" arrow button on the

        right side of the Network Bindings dialog. Move the adapter to make
        it the first in the list.
  

  5. Choose OK.

  NOTE: It doesn't matter which SNA Server in the domain is providing the "sponsor connection" for the SNA client software (the sponsor server is indicated when installing the SNA client software within the "primary" and "backup" servers when the "remote domain" option is selected). The client sponsor connection will work against either of these servers. However, this problem will prevent the client from opening a 3270 or APPC session through the servers.

STATUS

Microsoft has confirmed this to be a problem in SNA Server 2.1. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

KBCategory: kbnetwork kbsetup kbbug2.10 KBSubcategory: ntnetserv ntprotocol Additional reference words: prodsna 2.10 tcp/ip sockets

Last Reviewed: November 1, 1995