Cisco Certified Internetwork Expert (CCIE) Practice Test

What will happen if the PASV reply command includes 5 commas?

1. The connection will remain open

2. TCP connections will only be completed to ports from 1 to 1024

3. FTP clients will be able to determine the server's system type

4. The client must always send the PASV reply

The correct answer is: The connection will remain open

When the PASV reply in an FTP session includes five commas, it signifies that the server is indicating an IP address and port number for the data connection. Specifically, the typical PASV response format is "227 Entering Passive Mode (h1,h2,h3,h4,p1,p2)" where 'h1,h2,h3,h4' represent the server's IP address and 'p1,p2' represent the port number constructed from these two values. Having five commas in this sequence would denote that there is an extra segment that might be misinterpreted or not clearly defined, potentially signaling an issue with the response. However, the connection behavior resulting from this would likely lead to the connection remaining open because the communication process does not interrupt immediately; the client will still attempt to interpret the provided details. This can cause confusion or errors during the connection set up, but the open connection itself persists until resolved or closed by either party. The other answers focus on specific behaviors that do not directly relate to the implications of the PASV command structure. The limits on TCP ports and the nature of client-server communication do not pertain directly. Similarly, the statement about clients determining server type does not connect either, as that information is not part of