Exam 300-410 topic 1 question 76 discussion

I lab the given anwer is correct spoke be point to multpoint to that scenario work

as explanation why it is C: The output is from a spoke. You can tell at then end of the exhibit where it receives update from 192.168.1.1 (the OSPF RID of the hub router) and sends a packet to the other spoke router. The OSPF's adjacencies are not forming. Why? By default GRE tunnel interfaces are POINT-TO-POINT when enabled OSPF for a tunnel. In our case our spoke is trying to establish 2 adjacencies. One with the Hub router and one with the spoke. One adjacency is replacing the other, on the POINT-TO-POINT tunnel. So we need to make point-to-multipoint on our spoke. But if trying to form adjacency with other spoke, then other spoke is forming 2 adjacencies as well. so it needs point to multipoint as well.

Sorry, but i don't understand why it is not B. if you have metric type 1 in R2, it will add to the default cost of 20 the cost of the link to Isp2, isn't it? The cost of type 2 is always 20

C is correct

The correct answer is D. Look at the purple lines, this is Hub to Spoke, this is NOT Spoke to Spoke topology. So Option C is definitely not the answer.

Answer C: this linked helped a lot - https://community.cisco.com/t5/routing/help-with-ospf-and-dmvpn/td-p/2107338

we have two neigbors, beacuse is necesary point-to-multipoint

This is how I see it: The issue "Tunnel100 from EXCHANGE to DOWN, Neighbor Down: Adjacency forced to reset" is caused by OSPF default network type p2p. There is a different solution per DMVPN Phase. OSPF network type broadcast is suitable for phase 1 and 2, whereas point-to-multipoint is suitable for Phase3. We can exclude answers with p2p, like A and D. The solution needs to be applied on all spokes, so answer C is fitting best. https://community.cisco.com/t5/routing/help-with-ospf-and-dmvpn/td-p/2107338/page/2 https://networklessons.com/cisco/ccie-routing-switching/dmvpn-phase-1-ospf-routing

I believe C is correct

Ahh, again nothing is clear. So. Obviously, the problems are connected EXACTLY with the wrong type of network. I will assume that a point-to-point is configured, and the router needs to establish a neighborhood with two on the same interface, so it blinks(point-to-2point). Second. Why only on one spoke(is this a typical and highly scalable role for a router)? Of course for everyone. According to my logic, it turns out C. P.S.: Does anyone understand how to determine the phase here?

given answer is correct according to https://www.grandmetric.com/knowledge-base/design_and_configure/dmvpn-phase-3-single-hub-ospf-spoke-example/

the right answer is D. ip ospf network point-to-point on both spoke routers reference : https://learningspace.cisco.com/ Book title : ENARSI - Implementing Cisco Enterprise Advanced Routing and Services - Student Learning Guide, version=1.0.20, page 215 : "In strict hub-and-spoke DMVPNs, you should include the tunnel interface in the OSPF routing process, and configure the tunnel interface as a point-to-multipoint OSPF network type on the hub router, and as a point-to-point network type on the branch routers. In this case, there is no need to elect a DR on the DMVPN subnet."