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Disabling SPX Watchdog Packets

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Earl Welles
Novell Support Engineer

01 Jul 1997

Certain application such as NPRINTER, RPRINTER, and RCONSOLE use the SPX protocol, and its optional "watchdog" feature, to communicate. The watchdog transmits small system packets between a sender and a receiver so that the receiver of the packet knows the sender still exists. SPX Watchdog packets should not be confused with NCP Watchdog packets, which keep the user connection to a file server alive. Disabling SPX Watchdogs will not affect NCP Watchdog traffic.

In a WAN environment, when an on-demand line must be brought up to send SPX Watchdog packets, the watchdog packets can represent a considerable expense. Also, because the SPX Watchdog packets are not distinctly labeled, they are difficult for routers to "spoof". To solve this problem, Novell has provided a way to eliminate SPX Watchdog traffic. The solution requires that SPX Watchdogs be disabled on both sides of the SPX session.

On the Server Side

On the file server side, run SPXWDOG.NLM (available from the Novell Support Connection). This NLM adds to the NetWare environment a new SET parameter: SET SPX WATCHDOGS=ON | OFF. The default is ON. Setting this to OFF causes the file server side of the SPX session to stop initiating SPX Watchdog traffic. Note that the process which is sending SPX Watchdog packets (such as PSERVER) will need to be restarted before the setting takes effect.

On the Workstation Side

Even with the SET SPX WATCHDOGS=OFF setting in place, the workstation side will still send these packets and the server will respond. The workstation must also be set up so that it will not generate SPX Watchdog traffic. The way this is done depends on the client being used. (Note that the workstation will need to be rebooted for this setting to take effect.)

For NETX/VLM clients, add this parameter to the NET.CFG:


For Client32 for DOS/WINDOWS, add this parameter to NET.CFG:


For Client32 for Windows 95, click on the following in succession:

Start | Settings | Control Panel | Network | IPX 32-bit Protocol for Novell NetWare Client32 | Properties | SPX. Then uncheck the "Allow connection watchdogging" checkbox.

This setting is not available on the MS Windows NT or Apple Macintosh clients.

Be aware that with SPX Watchdogs disabled, the connection will not be deleted should one side or the other cease to exist (such as in a machine hang or power off) without the application terminating the connection.

* Originally published in Novell AppNotes


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