BGP MP-REACH attribute & MP-UNREACH attribute

Hello,

BGP-4 Update packets carry three IPv4-related attributes: NLRI (Network Layer Reachable Information), Next_Hop, and Aggregator. Aggregator contains the IP address of the BGP speaker that performs route summarization.

To carry information about multiple network layer protocols in NLRI and Next_Hop, MP-BGP introduces the following route attributes:

• MP_REACH_NLRI: indicates the multiprotocol reachable NLRI. It is used to advertise a reachable route and its next hop.

• MP_UNREACH_NLRI: indicates the multiprotocol unreachable NLRI. It is used to delete an unreachable route.

The preceding two attributes are optional non-transitive. Therefore, the BGP speakers that do not support MP-BGP will ignore the information carried in the two attributes and do not advertise the information to other peers.

https://support.huawei.com/hedex/hdx.do?docid=EDOC1100168821&id=EN-US_CONCEPT_0172354420&lang=en