Exam 350-501 topic 1 question 42 discussion

Actual exam question from Cisco's 350-501

Question #: 42
Topic #: 1

A remote operation center is deploying a set of I-BGP and E-BGP connections for multiple IOS-XR platforms using the same template. The I-BGP sessions exchange prefixes with no apparent issues, but the E-BGP sessions do not exchange routes. What causes this issue?

A. The I-BGP neighbors are mistyped and HELLO packets cannot be exchanged successfully between routers.
B. The E-BGP neighbors are not allowed to exchange Information due to the customer platform's default policy.
C. A PASS ALL policy has not been implemented for the I-BGP neighbors.
D. The next-hop-self command is not implemented on both E-BGP neighbors.

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Suggested Answer: B 🗳️

by 12_sdeEQ at April 6, 2023, 12:41 a.m.

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Duncan1016

7 months, 3 weeks ago

Selected Answer: B

External BGP (eBGP) neighbors must have an inbound and outbound policy configured. If no policy is configured, no routes are accepted from the neighbor, nor are any routes advertised to it. This added security measure ensures that routes cannot accidentally be accepted or advertised in the case of a configuration omission error. This enforcement affects only eBGP neighbors (neighbors in a different autonomous system than this router). For internal BGP (iBGP) neighbors (neighbors in the same autonomous system), all routes are accepted or advertised if there is no policy. https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r3-9/routing/configuration/guide/xr12krc39_chapter1.html

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12_sdeEQ

1 year, 1 month ago

Selected Answer: B

IOS-XR default setting is to drop eBGP announcements if not explicitely configured to do it.

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