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TCP / UDP NAT Endpoint Filtering options control how the router's NAT manages incoming connection requests to ports that are
already being used. Select one of the radio buttons.
End Point Independent Once a LAN-side application has created a connection through a specific port, the NAT will forward any
incoming connection requests with the same port to the LAN-side application regardless of their origin. This is the least restrictive
option, giving the best connectivity and allowing some applications (P2P applications in particular) to behave almost as if they are
directly connected to the Internet.
Address Restricted The NAT forwards incoming connection requests to a LAN-side host only when they come from the same IP
address with which a connection was established. This allows the remote application to send data back through a port different from
the one used when the outgoing session was created.
Port And Address Restricted The NAT does not forward any incoming connection requests with the same port address as an
already establish connection.
Note: Some of these options can interact with other port restrictions. Endpoint Independent Filtering takes priority over inbound filters
or schedules, so it is possible for an incoming session request related to an outgoing session to enter through a port in spite of an
active inbound filter on that port. However, packets will be rejected as expected when sent to blocked ports (whether blocked by
schedule or by inbound filter) for which there are no active sessions. Port and Address Restricted Filtering ensures that inbound filters
and schedules work precisely, but prevents some level of connectivity, and therefore might require the use of port triggers, virtual
servers, or port forwarding to open the ports needed by the application. Address Restricted Filtering gives a compromise position,
which avoids problems when communicating with certain other types of NAT router (symmetric NATs in particular) but leaves inbound
filters and scheduled access working as expected.
Enable Port Preservation: Check this box to enable Port Preservation. NAT Port preservation (on by default) tries to ensure that,
when a LAN host makes an Internet connection, the same LAN port is also used as the Internet visible port. This ensures best
compatibility for internet communications. Under some circumstances it may be desirable to turn off this feature.