Exam 350-401 topic 1 question 62 discussion

Correct answer TCP MSS & PMTUD

Some Sites will have this A. TCP MSScorrect B. IP MTU C. TCP window size D. DF bit Clear E. MTU ignore F. PMTUD the right answer will be TCP MSS & PMTUD

A - TCP Windows size -> Is not Correct. This happen between 2 host establissing a connexion. D - DF bit clear -> Is not Correct. DF = true if Bit value = 1, DF = false = means you can fragment -> if bit value = 0 (means clear), for that is incorrect inswer. E - MTU Ignore : Flse. The correct answer is B (IP MUT 1500 - GRE HEADER ) or use Jumbo Frames. and C (TCP MSS )

B & C are correct since only those answers are provided. if i had these answers; A. TCP window size B. IP MTU C. TCP MSS D. DF bit clear E. MTU ignore F. PMTUD then the answer will be C & F

if you clear DF bit allowing fragmentation you're breaking PMTUD, that relies on ICMP "fragmentation needed and DF set" message obviously TCP MSS and PMTUD (not present in this dump) https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html

BAD DUMP! Option B is PMTUD.

For this question B,C .. but now it comes with one more choise (PMTUD) and this is more accurate .. beacause IP MTU is not a GRE feature but a parameter that defines the maximum size of the IP packet that can be transmitted over a network path without fragmentation, so we can controll it to control the fragmentation. but PMTUD is a feature that detects the maximum transmission unit (MTU) of the path between two endpoints and adjusts the packet size to fit within that MTU

df = dont fragment, so if df is cleared, fragment is allowed

I;m going with B + C

Question is asking how to prevent not how to find.

voting. provided answer is correct

Options are: A. TCP window size B. TCP MSS C. IP MTU D. DF bit Clear E. MTU ignore F. PMTUD BE correct.

TCP MSS was used to find the MTU between the 2 end points. PMTUD is used to find the whole path most suitable MTU.

Only B+C make sense here but why the hell should these be "GRE features"??? Every second question is so bad expressed that I tend to skip the recertification.

https://en.wikipedia.org/wiki/Path_MTU_Discovery IP MTU allows the sending device to recognise and honour the configured value, TCP MSS is MSS clamping.

From my perspective df is cleared means df is set to zero. That means fragmentation is allowed through the GRE tunnel. Anyone else to add more or any rectification?