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Configuration Guide - IP Routing 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Configuration Guide - IP Routing

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Overview of BGP4+

Overview of BGP4+

BGP4+ controls route advertisement and selects optimal routes.

BGP4+ Definition

As a dynamic routing protocol used between ASs, BGP4+ is an extension of BGP.

Traditional BGP4 manages IPv4 routing information but does not support the inter-AS transmission of packets encapsulated by other network layer protocols (such as IPv6).

To support IPv6, BGP4 must have the additional ability to associate an IPv6 protocol with the next hop information and network layer reachable information (NLRI).

Two NLRI attributes that were introduced to BGP4+ are as follows:

  • Multiprotocol Reachable NLRI (MP_REACH_NLRI): carries the set of reachable destinations and the next hop information used for packet forwarding.

  • Multiprotocol Unreachable NLRI (MP_UNREACH_NLRI): carries the set of unreachable destinations.

The Next_Hop attribute in BGP4+ is in the format of an IPv6 address, which can be either a globally unique IPv6 address or a next hop link-local address.

Using multiple protocol extensions of BGP4, BGP4+ is applicable to IPv6 networks without changing the messaging and routing mechanisms of BGP4.


BGP transmits route information between ASs. It, however, is not required in all scenarios.

Figure 11-1 BGP networking

BGP is required in the following scenarios:

  • On the network shown in Figure 11-1, users need to be connected to two or more ISPs. The ISPs need to provide all or part of the Internet routes for the users. Routers, therefore, need to select the optimal route through the AS of an ISP to the destination based on the attributes carried in BGP routes.

  • The AS_Path attribute needs to be transmitted between users in different organizations.

  • Users need to transmit VPN routes through a Layer 3 VPN. For details, see the NE device Feature Description - VPN.

  • Users need to transmit multicast routes and construct a multicast topology. For details, see the NE device Feature Description - IP Multicast.

BGP is not required in the following scenarios:

  • Users are connected to only one ISP.

  • The ISP does not need to provide Internet routes for users.

  • ASs are connected through default routes.

Updated: 2019-01-14

Document ID: EDOC1100058916

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