Configure UPnP
The following are issues that can arise when using NAT:
•Some network applications assume the IP address and port that the client has been assigned are global routable values that can be used on the Internet directly. Often, this is not the case as the client has been assigned a private IP address that can only be used on the LAN.
•Other network applications send requests using a socket on a port “A” and expect to receive the reply from a different listening socket on port “Z”. When the NAT router creates a port mapping for port “A”, it won't know that it has to match it with the reply packets addressed to port “Z”.
•A number of network protocols assume they will always be able to use certain globally routable
NAT traversal techniques have been developed as a workaround to allow
– without the user having to manually configure port mapping.
NAT traversal relies on the discovery and control protocols that are part of the Universal Plug and Play (UPnP) architecture. The UPnP specification is based on TCP/IP and Internet protocols that let devices discover the presence and services offered by other UPnP devices in the network. It also supports the following, which are essential for NAT traversal:
•Learning public IP address
•Enumerating existing port mappings
•Adding and removing port mappings
•Assigning lease times to mappings
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