LinkScan Bug Status Report

DNS Lookup Failures

SYMPTOM
=======

LinkScan (all versions) running on Windows 2000 systems. 

Perhaps Windows XP systems as well (under investigation).

LinkScan erroniously reports significant numbers of DNS
Lookup Failures (LinkScan Status Code 900).

CAUSE
=====

This appears to be a problem with the Windows DNS Client
Service caching algorithms. Some (real) DNS lookup failures
are interpreted as a network failure. For a period of time, 
Windows reports DNS failures on many subsequent lookups. If
they cannot be resolved from cache, it seems that Windows
does not actually attempt the lookups since it wrongly
assumes the network is unavailable. 

SOLUTION
========

Disable the Network Failure Cache by editing the System
Registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters

NetFailureCacheTime

Set NetFailureCacheTime to 0 (zero).

Reboot the system (or stop and restart the DNS Client Service).


If you still experience problems, contact linkscan@elsop.com
for a LinkScan patch that incorporates some additional 
protections against false DNS reports. These changes are
included in LinkScan 9.0f and later.

Please report any new problems via our Support Page