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Juniper JN0-664 Exam - Topic 2 Question 55 Discussion

In which two ways does OSPF prevent routing loops in multi-area networks? (Choose two.)
C) All areas are required to connect to area 0. and D) The SPF algorithm prunes looped paths within an area.
A) All areas are required to connect as a full mesh.
B) The LFA algorithm prunes all looped paths within an area.

Juniper JN0-664 Exam - Topic 2 Question 55 Discussion

Actual exam question for Juniper's JN0-664 exam
Question #: 55
Topic #: 2
[All JN0-664 Questions]

In which two ways does OSPF prevent routing loops in multi-area networks? (Choose two.)

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Suggested Answer: C, D

OSPF is an interior gateway protocol that uses link-state routing to exchange routing information among routers within a single autonomous system. OSPF prevents routing loops in multi-area networks by using two methods: area hierarchy and SPF algorithm. Area hierarchy is the concept of dividing a large OSPF network into smaller areas that are connected to a backbone area (area 0). This reduces the amount of routing information that each router has to store and process, and also limits the scope of link-state updates within each area.All areas are required to connect to area 0 either directly or through virtual links2. SPF algorithm is the method that OSPF uses to calculate the shortest path to each destination in the network based on link-state information. The SPF algorithm runs on each router and builds a shortest-path tree that represents the topology of the network from the router's perspective.The SPF algorithm prunes looped paths within an area by choosing only one best path for each destination3.


by Pok at Nov 25, 2025, 09:26 PM

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Latosha
3 months ago
C is a must, but I’m torn on D. What about B?
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Marg
3 months ago
I lean towards C and D as well. They prevent loops effectively.
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Ben
3 months ago
I feel like A is misleading. Full mesh isn't required.
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Kris
4 months ago
Not sure about D. Isn't it more about the SPF algorithm?
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Lakeesha
4 months ago
I agree, C is definitely one. D makes sense too.
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Remedios
4 months ago
I think C and D are the right answers. Area 0 is crucial.
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Billye
5 months ago
Wait, are all areas really required to connect as a full mesh? That sounds off.
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Mabel
5 months ago
SPF algorithm is crucial for pruning loops, no doubt.
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Albert
5 months ago
I thought the LFA algorithm was for fast reroute, not loop prevention?
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Chau
5 months ago
Definitely agree, that's a key point!
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Arthur
5 months ago
OSPF requires all areas to connect to area 0.
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Ettie
5 months ago
Haha, A is a good one. A full mesh of areas, really? That would be a nightmare to configure.
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Alexis
6 months ago
C and D make the most sense to me. Can't have loops in OSPF!
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Dorian
6 months ago
I thought B was the answer. The LFA algorithm sounds like it would do the trick.
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Lisbeth
6 months ago
I feel like I’ve seen something about areas needing to connect in a full mesh, but that doesn’t sound right for OSPF.
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Felice
6 months ago
I’m a bit confused; I thought the LFA algorithm was more about fast reroute rather than loop prevention.
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Kandis
6 months ago
Ah, I remember learning about this in class. OSPF uses the concept of areas, and all areas have to connect to the backbone area 0 to prevent routing loops across the entire network. The SPF algorithm also helps identify and remove any looped paths within a single area. I'll go with C and D.
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Mireya
6 months ago
I'm pretty confident on this one. OSPF prevents loops by requiring all areas to connect to the backbone area 0, and the SPF algorithm helps identify and remove any looped paths within an area. I'll select C and D.
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Isaac
7 months ago
C and D are the correct answers. The OSPF area 0 requirement and the SPF algorithm are key to preventing routing loops.
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Kasandra
7 months ago
Hmm, this is a tricky one. I know OSPF has some mechanisms to prevent loops, but I'm not totally clear on the details. I'll have to think this through carefully and use the process of elimination to narrow down the options.
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Mable
7 months ago
I remember practicing a question about OSPF and the SPF algorithm, so I think that might be one of the answers for preventing loops.
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Emiko
7 months ago
D is definitely the way to go. The SPF algorithm is the bread and butter of OSPF loop prevention.
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Sherman
7 months ago
I think one way OSPF prevents loops is by requiring all areas to connect to area 0, but I'm not entirely sure about the second option.
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Gracia
8 months ago
Okay, I think I've got this. OSPF uses the concept of areas to prevent loops, with all areas required to connect to the backbone area 0. And the SPF algorithm helps prune any potential looped paths within an area. I'll go with C and D.
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Lilli
8 months ago
I'm pretty sure the answer has something to do with the OSPF area structure, but I'm not sure exactly how it prevents loops. I'll need to review the OSPF concepts again.
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Carol
2 months ago
So, C and D are the right choices then?
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Felicidad
2 months ago
Yes, it prunes those looped paths effectively.
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Dorothy
3 months ago
And the SPF algorithm helps too, right?
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Carlene
3 months ago
Definitely! That’s how OSPF maintains a backbone.
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Lenna
3 months ago
I think connecting all areas to area 0 is key.
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