Draytek VigorPro 5500 Series User Manual page 109

The reminder as regards concern about Firewall and UPnP
Can't work with Firewall Software
Enabling firewall applications on your PC may cause the UPnP function not
working properly. This is because these applications will block the accessing
ability of some network ports.
Security Considerations
Activating the UPnP function on your network may incur some security threats.
You should consider carefully these risks before activating the UPnP function.
Some Microsoft operating systems have found out the UPnP weaknesses and
hence you need to ensure that you have applied the latest service packs and
patches.
Non-privileged users can control some router functions, including removing
and adding port mappings.
The UPnP function dynamically adds port mappings on behalf of some
UPnP-aware applications. When the applications terminate abnormally, these
mappings may not be removed.
VigorPro5500 Series User's Guide 101