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Exam JN0-663 topic 1 question 70 discussion

Actual exam question from Juniper's JN0-663
Question #: 70
Topic #: 1
[All JN0-663 Questions]


A Layer 3 VPN exists in the provider network and the CE devices are connecting to the PE devices using BGP. The PE devices are receiving BGP routes from the
CE devices and the PE devices have the CE BGP routes in their respective routing tables. However, the remote CE devices are not receiving the BGP routes.
Referring to the exhibit, what is the problem?

  • A. A route distinguisher mismatch exists.
  • B. The PE devices are detecting an AS loop.
  • C. The CE devices are detecting an AS loop.
  • D. A VRF target community mismatch exists.
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️
by sandpit at Dec. 7, 2021, 10:54 p.m.

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sandpit
Highly Voted 3 years, 4 months ago
The answer should be PE devices are detecting AS Loop.
upvoted 11 times
zakhar
3 years, 4 months ago
I agree PE devices are detecting loop, thats why knobs like as-override or advertise-peer-as exist!
upvoted 5 times
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jncie_examer
Most Recent 2 years, 6 months ago
Selected Answer: B
CE is not receiving. CE settings don't really matter at this point.
upvoted 2 times
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Totalstranger
2 years, 8 months ago
Selected Answer: B
B is the way
upvoted 1 times
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BobbyAxelrod
2 years, 11 months ago
Selected Answer: B
Agree with Sandpit
upvoted 3 times
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dodds
3 years ago
I think the answer is C. PE still advertises routes, but CPE discards these routes because it's detecting an as loop. https://netdevops.me/2015/11/basic-l3vpn-bgpmpls-vpn-or-vprn-configuration-alcatel-lucent-juniper/
upvoted 1 times
dodds
2 years, 11 months ago
Changed my mind, it's B By default, Junos OS does not advertise the routes learned from one EBGP peer back to the same external BGP (EBGP) peer. In addition, the software does not advertise those routes back to any EBGP peers that are in the same AS as the originating peer, regardless of the routing instance. https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/ref/statement/advertise-peer-as-edit-protocols-bgp.html
upvoted 2 times
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dexjov
3 years ago
i also think it's B, CE devices are not receiving routes because PE by default do not advertise BGP routes into AS that is already in route's AS path
upvoted 2 times
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ptt
3 years, 1 month ago
CE devices are not "RECEIVING" the BGP routes. That means PE detecting the Loop and might to be configured the knod "advertise-peer-as". I will select B.
upvoted 3 times
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oceans1908
3 years, 2 months ago
C is correct loop prevention works on the local BGP router. Assuming the pe ce is an eBGP peering.
upvoted 1 times
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C (25%)
B (20%)
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