Exam 350-401 topic 1 question 285 discussion

C is correct B is wrong cause you need an extended access-list to accomplish this

The key is the access list number as it is extended access list and word established

Correct is C. The purpose of using the established keyword is to allow the return traffic of an established connection, while denying any new connection attempts. This can be useful in scenarios where you want to allow responses from outbound connections initiated from within your network while still maintaining security by not allowing new inbound connections on that port. With the given ACL rule in the answer options, it is clear that we are talking about FTP Server which uses port 21. If a client from inside the network initiates an FTP connection to an external FTP server (which typically uses port 21 for control), the firewall would allow the returning control traffic from the FTP server due to the established keyword.

extended access lists allow ports whereas standards dont

it is a extendend access-list Standard 1–99 and 1300–1999 Extended IP 100–199 and 2000–2699

correct answer

B and D are Numbered ,standared ACL, (0-99) Numbered, standered ACL does not filter the trafic type (TCP,UDP, IP,ICMP,TCP.....)

The correct answer is C because the ACL contains the source and destination (it's an extended ACL).

The given answer is correct