Cautions With Upnp - ZyXEL Communications P-663HN-51 User Manual

6.4.3 Cautions with UPnP

The automated nature of NAT traversal applications in establishing their own
services and opening firewall ports may present network security issues. Network
information and configuration may also be obtained and modified by users in some
network environments.
When a UPnP device joins a network, it announces its presence with a multicast
message. For security reasons, the ZyXEL Device allows multicast messages only
on the LAN.
All UPnP-enabled devices may communicate freely with each other without
additional configuration. Disable UPnP if this is not your intention.
You must have IIS (Internet Information Services) enabled on the Windows web
server for UPnP to work.
P-663HN-51 User's Guide
Chapter 6 LAN Setup
79