H12-891_V1-0 practice question 4 of 35

The following description of MP-BGP is incorrect?( Single choice questions).

Full set: 607 questions

Answer options

A: The MP_UNREACH_NLRl of the update message, excluding the path nationality.

B: MP-BGP can be used to assign tags.

C: MP_REACH_NLRI and MP_UNREACIH_NLRI are optional transition properties. Correct answer

D: A complete MP_REACH_NLRI attribute structure contains address family, next hop, and prefix information.

Correct Answer:

C. MP_REACH_NLRI and MP_UNREACIH_NLRI are optional transition properties.

Explanation

The statement that MPREACHNLRI and MPUNREACHNLRI are optional transitive attributes is incorrect. According to RFC 4760, which defines Multiprotocol Extensions for BGP-4, both the MPREACHNLRI (attribute code 14) and MPUNREACHNLRI (attribute code 15) attributes are defined as Optional Non-Transitive. This means if a BGP speaker does not support the multiprotocol extensions, it will ignore these attributes and will not pass them on to its peers.

Why Incorrect

A: The MPUNREACHNLRI attribute is used to withdraw routes and only contains the prefixes to be withdrawn; it does not carry path attributes. B: MP-BGP is commonly used in MPLS VPN scenarios to carry VPNv4 routes, which include MPLS labels (often referred to as tags). D: The MPREACHNLRI attribute structure correctly includes the Address Family (AFI/SAFI), next-hop information, and the NLRI (prefixes).

References

- RFC 4760, "Multiprotocol Extensions for BGP-4", Section 3, "Multiprotocol Capability Negotiation", specifies that the MPREACHNLRI and MPUNREACHNLRI attributes are Optional and Non-Transitive.

- Huawei HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Training Material, "MP-BGP", Section on MP-BGP Attributes.

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