diff -ur twiki/lib/TWiki.cfg twiki_patched/lib/TWiki.cfg
--- twiki/lib/TWiki.cfg	2004-08-31 11:35:19.000000000 -0500
+++ twiki_patched/lib/TWiki.cfg	2005-03-31 11:41:14.000000000 -0600
@@ -361,6 +361,10 @@
 $logFilename        = "$logDir/log%DATE%.txt";
 #                   Pathname of remote users file that maps IP to user :
 $remoteUserFilename = "$dataDir/remoteusers.txt";
+#                   Comma separated list of IPs and Networks that are allowed to
+#                   be remembered. Keep it blank to remember all IPs
+#                   Example: $remoteUserNets = '10.1.0.0/16,192.168.0.0/16';
+$remoteUserNets = '';
 #                   %WIKIUSERSTOPIC% : Name of users list topic :
 $wikiUsersTopicname = "TWikiUsers";
 #                   Pathname of WebUsers topic, used to map Intranet login name
diff -ur twiki/lib/TWiki.pm twiki_patched/lib/TWiki.pm
--- twiki/lib/TWiki.pm	2004-11-19 23:31:53.000000000 -0600
+++ twiki_patched/lib/TWiki.pm	2005-03-31 11:41:13.000000000 -0600
@@ -62,7 +62,7 @@
         $scriptUrlPath $pubUrlPath $pubDir $templateDir $dataDir $logDir
         $siteWebTopicName $wikiToolName $securityFilter $uploadFilter
         $debugFilename $warningFilename $htpasswdFilename
-        $logFilename $remoteUserFilename $wikiUsersTopicname
+        $logFilename $remoteUserFilename $remoteUserNets $wikiUsersTopicname
         $userListFilename $doMapUserToWikiName
         $twikiWebname $mainWebname $mainTopicname $notifyTopicname
         $wikiPrefsTopicname $webPrefsTopicname
@@ -1104,6 +1104,28 @@
         return $remoteUser;
     }
 
+    # Only remember if $remoteAddr within $remoteUserNets
+    if( defined $remoteUserNets and $remoteUserNets ne '' ) {
+        require NetAddr::IP;
+        my $match = 0;
+        foreach my $netstr ( split( /,/, $remoteUserNets ) ) {
+            my $net = new NetAddr::IP $netstr;
+
+            if( ! defined $net ) {
+                writeWarning "$netstr is not a valid IP Network address in \$remoteUserNets. Please fix in TWiki.cfg.";
+                next;
+            }
+            if( $net->contains( new NetAddr::IP $remoteAddr ) ) {
+                $match = 1;
+                last;
+            }
+        }
+        if( ! $match ) {
+            return $remoteUser;
+        }
+    }
+
+
     my $text = &TWiki::Store::readFile( $remoteUserFilename );
     # Assume no I18N characters in userids, as for email addresses
     # FIXME: Needs fixing for IPv6?