RRAS with Multicast and Unicast


We are running Windows Server 2003 (standard) with RRAS and NAT installed.
Everything seems to work fine, all machines that are behind the server can
access the Internet, with just one exception. It seems not to be possible to
view streaming media on all ports other then 80. When clicking on a link to
a movie for example, there's an error message that says the server or
network is not available.

After passing some tests with our ISP, it seems that the router is blocking
the necessary ports for Unicast and Multicast broadcasts. How can this be
solved? In the RRAS MMC snap-in, there are 2 NIC's visible, the one for the
Internet and the other one for the LAN, where exactly can one add (or open)
ports for certain applications? I suppose it is on the Internet adapter that
this must be done, but I have no idea where exactly.

All help greatly appreciated.

Best Regards,