Conventional BGP-4 manages only IPv4 unicast routing information, and inter-AS transmission of packets of other network layer protocols, such as multicast, is limited.

To support multiple network layer protocols, the Internet Engineering Task Force (IETF) extends BGP-4 to Multiprotocol Extensions for BGP-4 (MP-BGP). MP-BGP is forward compatible. Specifically, routers supporting MP-BGP can communicate with the routers that do not support MP-BGP.

As an enhancement of BGP-4, MP-BGP provides routing information for various routing protocols, including IPv6 (BGP4+) and multicast.
  • MP-BGP maintains both unicast and multicast routes. It stores them in different routing tables to separate unicast routing information from multicast routing information.

  • MP-BGP supports both unicast and multicast address families and can build both the unicast routing topology and multicast routing topology.

  • Most unicast routing policies and configuration methods supported by BGP-4 can be applied to multicast, and unicast and multicast routes can be maintained according to these routing policies.

Extended Attributes

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.

Address Family

The Address Family Information field consists of a 2-byte Address Family Identifier (AFI) and a 1-byte Subsequent Address Family Identifier (SAFI).

BGP uses address families to distinguish different network layer protocols. For the values of address families, see relevant standards. The NetEngine 8000 F supports multiple MP-BGP extension applications, such as VPN extension and IPv6 extension, which are configured in their respective address family views.

For details about MP-BGP in multicast, see the HUAWEI NetEngine 8000 F Series Router Feature Description > IP Multicast.

For details about the BGP VPNv4 address family and BGP VPN instance address family, see the HUAWEI NetEngine 8000 F Series Router Feature Description > VPN.

Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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