Which type of port is used by a client when it establishes a TCP connection?
A.
Ephemeral
1D0-470
B.
Well-known
C.
Reserved
D.
Static
Explanation:
When a connection is established the client side of the connection must use a source port number. Unless a client program explicitly requests a specific port number, the port number used is an ephemeral port number. Ephemeral ports are those ports above 1023 (1024-65535). These ports are dynamically assigned to the client, and released by the client. Once released, these ports may be used again by a different client.
Incorrect Answers:
B: A client could explicitly use a well-known TCP port. The default behavior, however, is to use a ephemeral port.
C: A reserved port is a port that is not yet assigned, and should not be used unless a formal assignment has been made by registering the port with the appropriate Internet registry service.
D: A static port is a port that is always open or closed. A dynamic port is a port that opens when it is assigned to a client or service, and then closes when the service or client releases the port. Dynamic ports are used in environments such as firewalls and proxy servers to hide ports and services, for example to limit the findings of a port scanner.