X.25 Connection Appears Active After Cable Disconnected

ID: Q222545

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 3.0SP1, 3.0SP2, 3.0SP3, 4.0, 4.0SP1, 4.0SP2

SYMPTOMS

An X.25 connection to a remote device (that is, mainframe) may not generate a connection outage when the X.25 cable is disconnected from a X.25 adapter installed in an SNA Server system. SNA Server Manager continues to show the connection in an Active state even after the cable is disconnected. The following event may be logged in the Windows NT Application Event Log on the SNA Server system when this occurs:

Event ID: 325
Source: SNA X.25 Link Service
Description: Driver <link service driver name> DSR has gone OFF: probable modem failure.

All active sessions using the X.25 connection will be lost when the X.25 cable is disconnected from the X.25 adapter even though the connection appears to be active when looking at its status in SNA Server Manager.

NOTE: This problem may occur with any X.25 adapter that uses SNA Server's Ibmx25.dll "dumb card" driver interface. This driver interface is published in the appendix of the SNA Device Interface Specification (SNADIS) guide, which is included in the SNA Server SDK.

CAUSE

A connection outage is not generated when the X.25 cable is disconnected from the X.25 adapter because an incorrect variable is passed to the function that is responsible for generating the outage. The result is that an outage is not generated, which means that the X.25 link service does not inform the SNA Server service that the connection has been lost. Therefore, the connection appears to remain active even though it is no longer active.

RESOLUTION

To resolve this problem, obtain the latest service pack for SNA Server version 4.0. For additional information, please see the following article in the Microsoft Knowledge Base:

Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack

STATUS

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1, and 4.0 SP2. This problem was first corrected in SNA Server version 4.0 Service Pack 3.

MORE INFORMATION

Host connection failures normally result in a connection outage error. When a connection outage is generated, the status of the connection will change to either Pending or Inactive when viewed in SNA Server Manager. In addition, an Event 23 message is logged in the Windows NT Application Event Log when a link service detects an outage. The Event 23 message includes a connection specific qualifier (that is, return code) that indicates the type of failure that occurred. The following are some of the common X.25 connection outages that may occur:

X'37' - Loss of a virtual circuit.

X'60' - The switched virtual circuit to the host has been cleared down (broken) either by the host or by the X.25 network itself.

X'61' - The permanent virtual circuit to the host has been cleared down (broken) either by the host or by the X.25 network itself.

X'62' - An attempt to connect to the host through a switched virtual circuit has failed.

As an example, an X.25 link service will log the following message when the cable between the modems is disconnected:

Event ID: 23
Source: SNA X.25 Link Service
Description: Connection <connection_name> using Link Service <link_service_name> failed.

Qualifier = X'61'

After applying this update, the X.25 link service will generate an outage when the X.25 cable is disconnected from the X.25 adapter.

Additional query words:

Keywords : sna4sp3fix
Version : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1,4.0SP2
Platform : WINDOWS
Issue type : kbbug