From: DeskNow Knowledge Base
http://www.desknow.com/kb/

On Linux/Unix, DeskNow seems to cache DNS results forever
http://www.desknow.com/kb/idx/16/121/article/

The default Java installation caches DNS results forever, to prevent DNS spoofing attacks. This is a very conservative measure, which is nonetheless the default in Java.

If you installed your own Java to run DeskNow, you may still have these security settings - the Java setup that ships with DeskNow for windows does not.

To limit DNS caching to 5 minutes, simply edit the file /usr/java/jdk1.5.0_06/jre/lib/security/java.security and add the following line:

networkaddress.cache.ttl=300

then restart DeskNow