How does one to this?

Background: I use DynDNS for a little test server connected via 'almost-always-on' dial-up ISDN connection. The connection breaks rather often (once a day or two), so the server's IP doesn't last very long. I left 'keep DNS translation in cache' field on DynDNS at default 60 seconds, but my WinXP workstation keeps server's old IP for hours, regardless. If I reboot the workstation, I get the 'fresh', correct IP for the server, of course, but that is hardly convenient. Is there a way to force WinXP to flush its IP cache and do fresh DNS lookup?

Thanks!

Edit: found:

ipconfig /flushdns