Exam 300-410 topic 1 question 262 discussion

This is actually to my surprise... The TFTP apparently is using the random port for the transfer: TFTP uses UDP as its transport protocol. A transfer request is always initiated targeting port 69, but the data transfer ports are chosen independently by the sender and receiver during the transfer initialization. The ports are chosen at random according to the parameters of the networking stack, typically from the range of ephemeral ports.[4] https://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol

C is corerct

This is interesting. Huntkey provided a nice resource of information, the RFC for TFTP provides explanation as to why this rule actually affects the connection between client and server. Based on the RFC, TFTP utilizes an ephemeral port named (TID, Transfer Identifier) that is used for the duration of the session. This TID is a random port between 0 to 65535. When a client sends a Write or Read request (WRQ and RRQ respectively), the Client chooses a TID at random, and sends the request to the server with destination port 69, this is allowed by the ACE #2 in the ACL. When the server receives the Request, it also chooses a TID at random, and uses that to send the ACK for a WRQ or a the first data packet for RRQ, but this communication is now continued between TIDs as the source/destination UDP ports. this is where the ACE#3 in the ACL is breaking the connection. 1.- CLIENT (src.port.TID) ---(WRQ/RRQ)----> (dst.port.69) TFTP 2.- CLIENT (dst.port.TID) <---(ACK/DATA)--- (src.port.TID) TFTP

D correct: https://thwack.solarwinds.com/free-tools-trials/f/tftp-server/4613/tftp-communicating-on-high-ports

This doesn't make sense the ACL is applied 'in' what does it have to do with outbound traffic ?