About ports. Watchguard Firebox X4500, Firebox X Edge e-Series

Introduction to Network Security

About ports

Although computers have hardware ports you use as connection points, ports are also numbers used to map traffic to a particular process on a computer. These ports, also called TCP and UDP ports , are where programs transmit data. If an IP address is like a street address, a port number is like an apartment unit number or building number within that street address. When a computer sends traffic over the Internet to a server or another computer, it uses an IP address to identify the server or remote computer, and a port number to identify the process on the server or computer that receives the data.

For example, suppose you want to see a particular web page. Your web browser attempts to connect to port

80 (the port used for HTTP traffic) on the IP address of the web server. When it makes the connection, your web browser sends the request for the web page and gets it from the web server. Both computers then end the connection.

Many ports are used for only one type of traffic, such as port 25 for SMTP (Simple Mail Transfer Protocol). Some protocols, such as SMTP, have ports with assigned numbers. Other programs are assigned port numbers dynamically for each connection. The IANA (Internet Assigned Numbers Authority) keeps a list of well-known ports. You can see this list at: http://www.iana.org/assignments/port-numbers .

For information on ports used by WatchGuard products and Microsoft products, see the Reference Guide . Most policies you add to your Firebox configuration are given a port number in the range from 0 to 1024, but possible port numbers range from 0 to 65535.

6 Firebox X Edge e-Series