Exam 200-301 topic 1 question 372 discussion

I hate this

Correct is D Pay attention to the statement: "establishes the OSPF neighbor relationship without forming an adjacency" This two conditions (1) NO Neighbor Missing AND (2) no adjacency occurs only in two situations: 1) Neighboring interfaces with MTU mismatch. 2) Neighboring interfaces with OSPF network type mismatch https://learning.oreilly.com/library/view/ccna-200-301-official/9780136755562/vol1_ch21.xhtml

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Hello guys, read this article for a clear expanded answer to this question : https://learningnetwork.cisco.com/s/question/0D56e0000CfMTBnCQO/which-action-establishes-the-ospf-neighbor-relationship-without-forming-an-adjacency

D is correct

A is correct

In my opinion - establishes the neighbor relationship without forming an adjacency could be two things. 1. MTU mismatch allows the routers to move past the two-way state but gets stuck in the EXSTART state. This is an ERROR condition. So I go with 2. setting the priority on two routers to 0 allows the routers to maintain a two-way state (non-error condition) but not move to the full state (DROTHERs).

It's A, because if you modify the network type from Broadcast, you are guaranteeing they will be adjacent. In OSPF, two routers become adjacent in only two scenarios: 1) At least one of them is a DR or BDR in a broadcast network, OR 2) It is a point-to-point or multi-access network. So if we change the network type here, we are guaranteeing #2.

Okay; there's a lot of ambiguity in the comments. The bottom line is that it *has* to be A for the simple reason that the only way for a neighbor relationship to be established at all is if the hello timers match. The question asks "Which action establishes the OSPF neighbor relationship without forming an adjacency?" If you don't change the hello interval to match, there are no other situations under which the neighbor relationship will form. It's badly written but the answer is certainly A, as "OSPF requires that both hello and dead timers be identical for all routers on the segment to become OSPF neighbors." https://www.ciscopress.com/articles/article.asp?p=2294214

Question's Answer: Choosing answer A (modify hello interval) will cause R1 and R2 to successfully get to the 2-WAY OSPF neighbor relationship state but R1 and R2 will not become adjacent neighbors. Because R4 and R3 have the highest and second highest OSPF Router-IDs (192.168.1.4 and 192.168.1.3), they will become the DR and BDR. R1 will form full adjacencies with both the DR and BDR. https://learningnetwork.cisco.com/s/question/0D56e0000CfMTBnCQO/which-action-establishes-the-ospf-neighbor-relationship-without-forming-an-adjacency?t=1683708512442

NOT possible - NO right answered if we get all request conditions. First of all, "B. modify process ID" has nothing to do with relationship between devices, is internal. To establishes the OSPF neighbor relationship we need to change timers to be the same. No matter if routers are in Broadcast or P2P, they cannot become neighbors if timers are not the same (even the Hello packets are transmitted, they will be ignored). With presented settings if we adjust timers the routers will form ADJACENCY (again no matter if network types are Broadcast or P2P). The only way to force routers to not form adjacency is to change PRIORITY to 0. In this way the routers will not become DR/BDR and will remain both DROTHERs (Neighbor Count is 1, Adjacent neighbor count is 0). They will continue to send Hello messages, will be neighbors, but never achieve adjacency. So, regarding the question there are 2 necessary actions to take to fulfill the request: changing timers to be the same & priority 0. With only one action is impossible. Tested all variants in PT. Regards to the person who invented this impossible question/situation,

I've gone back and forth on this question, but I have to finally go with A. If you change the network type, the Hello and Dead Interval timers still will not match, so a neighbor relationship still will not form. So A is the only possible answer (assuming that if you change the Hello timer, IOS automatically makes the Dead Interval timer 4 times that of the Hello timer, can anyone confirm that?). I don't really know WHY it's A, because why then would they not reach full adjacency? I wonder if it has something to do with the fact that one router interface does not display any "attached" statement ("Attached via network statement", "Attached via interface enable")? I have no idea....

Ok. I'll take a swing at this. The question should have been "Which TWO actions establish..". Then it would have made perfect sense! A & D.

I have rebuild this on real switches and A is the correct answer. When you modify the hello timer on R2 to 10 the output is: Neighbour Count is 1, Adjacent neighbour count is 0

Answer is D. From the perspective of OSPF, there are a couple of things that must match for an OSPF neighborship to establish; these include: 1. The devices must be in the same area. 2. The devices must have the same authentication configuration. 3. The devices must be on the same subnet. 4. The devices hello and dead intervals must match. 5. The devices must have matching stub flags. But the question is asking about OSPF neighborship without forming adjacencies. The OSPF point-to-point and point-to-multipoint nonbroadcast networks require statically defined neighbor statements without forming DR/BDR adjacencies.

A https://community.cisco.com/t5/switching/ospf-neighbor-v-ospf-adjacency/td-p/1576785#:~:text=An%20OSPF%20adjacency%20is%20formed,routing%20updates%20from%20the%20DR.

https://www.ciscopress.com/articles/article.asp?p=2294214 spend time reading this one and you will know the best answer