User`s guide

MN-700 Base Station Configuration Guide 22
About Ports
Data ports play an important role in data transmission.
Many different types of data are transmitted across a network, and certain types of data must pass out of certain
ports. The data type is identified by the protocol, or rules, that it follows. Typically, the data protocol determines the
ports to which the data is passed. For example, when you download files by using the File Transfer Protocol (FTP),
the request goes to outbound port 21, and the response returns to inbound port 20.
As a security feature, the Microsoft base station only opens inbound ports when data is transmitted from one of the
computers or other devices on your local network to the corresponding outbound port.
By keeping the inbound ports closed, the base station protects your networked computers from unsolicited traffic
from the Internet. A computer on the wide area network cannot initiate communication with your computers.
In certain situations, however, you may need to change the port configuration of the base station.
To run a program that uses a different port for inbound traffic than for outbound traffic, you may need to configure
application-triggered port forwarding.
To host a server on your network that receives unsolicited data requests from the Internet, you must configure
persistent port forwarding.
Application-Triggered Port Forwarding
Some applications, such as Internet games and videoconferencing, require multiple ports for data transmission.
For example, when you download files by using the File Transfer Protocol (FTP), the data requests go out through
port 21, and responses return through port 20.
These multiple port transmissions might cause problems when NAT is enabled on your base station, because the
NAT service anticipates that data sent to one port will return to the same port.
To run a program that uses a different port for inbound traffic than for outbound traffic, you may need to configure
application-triggered port forwarding.
The following illustration shows the Application-Triggered Port Forwarding page of the Base Station
Management Tool.