The Windows Firewall: Allow UPnP framework exception setting allows a computer to receive unsolicited Plug and Play messages sent by network devices, such as routers with built-in firewalls. To receive these messages, Windows Firewall opens TCP port 2869 and UDP port 1900. If you enable this policy setting, Windows Firewall opens these ports so that the computer can receive Plug and Play messages. You must specify the IP addresses or subnets from which these incoming messages are allowed. If you disable this policy setting, Windows Firewall blocks these ports and prevents the computer from receiving Plug and Play messages.