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Exam JN0-663 topic 1 question 72 discussion

Actual exam question from Juniper's JN0-663
Question #: 72
Topic #: 1
[All JN0-663 Questions]

Which two statements about virtual links are correct? (Choose two.)

  • A. Virtual links are point-to-point.
  • B. Virtual links are used for control plane traffic.
  • C. Virtual links are excluded from SPF calculations.
  • D. Virtual links are bidirectional.
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Suggested Answer: AB 🗳️

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anonymonkey
Highly Voted 3 years, 8 months ago
A&D, Virtual links are essentially ptp tunnels allowing two nonconnected area 0s to communicate. This tunnel is used to send LSA's as type 7, can be converted to type 5 further down the network so def not ignored, and data between discontiguous area 0s.
upvoted 5 times
anonymonkey
3 years, 8 months ago
discontiguous non area 0s. (areas not able to connect directly to area zero therefore must tunnel though a non area 0 network to reach area 0)
upvoted 1 times
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mohdema
Most Recent 2 years, 4 months ago
Selected Answer: AB
From Juniper Official Book: Remember that a virtual tunnel is a control plane feature only. SPF will still calculate the shortest physical path between two points, which might not be the same path as the virtual tunnel. No need to mention also that all VL connections are all P2P.
upvoted 1 times
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mohdema
2 years, 4 months ago
Selected Answer: AC
Virtual links are to allow traffic, they are added in the routing table and they are pt2pt They are not excluded from the SPF VIRTUAL LINKS ARE BIDIRECTIONAL For backbone areas only, create a virtual link to use in place of an actual physical link. All area border routers and other routing devices on the backbone must be contiguous. If this is not possible and there is a break in OSPF connectivity, use virtual links to create connectivity to the OSPF backbone. When configuring virtual links, you must configure links on the two routing devices that form the end points of the link, and both of these routing devices must be area border routers. You cannot configure links through stub areas. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/47866-ospfdb7.html
upvoted 1 times
mohdema
2 years, 4 months ago
I was wrong it's AB
upvoted 1 times
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DIbyam
2 years, 6 months ago
Agree with A&B. https://community.cisco.com/t5/routing/ospf-virtual-link/td-p/4499678
upvoted 1 times
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amrkhater899
2 years, 8 months ago
Selected Answer: AB
Correct Answer: A&B From Juniper Official Book: Remember that a virtual tunnel is a control plane feature only. SPF will still calculate the shortest physical path between two points, which might not be the same path as the virtual tunnel. No need to mention also that all VL connections are all P2P.
upvoted 4 times
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BobbyAxelrod
2 years, 11 months ago
Selected Answer: AC
Agree with mikkamilla
upvoted 1 times
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Sct38
3 years, 4 months ago
Not used to tunnel customer traffic, just extends OSPF control plane traffic between nodes for SPF calculaton. Hence B is correct and C is wrong. Not bidirectional, as requires virtual link to be setup on both sides for it to work. Answer A+B
upvoted 4 times
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mikkamilla
3 years, 10 months ago
A and C When you stitch areas via Virtual Links is because you need data plane traffic to go through it. On the other side, the devices on both ends of the tunnel will think they're ABR and use the normal LSAs for LSDB computations. There's no knowledge of virtual links in the ospf database https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/47866-ospfdb7.html
upvoted 4 times
anonymonkey
3 years, 8 months ago
Can be configured not to be redistributed but is not the default. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/9237-9.html
upvoted 1 times
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A (35%)
C (25%)
B (20%)
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