Mp-Bgp - HPE 5800 Series Configuration Manual

Figure 65 Confederation network diagram
A non-confederation BGP speaker is not required to know sub-ASs in the confederation. It
considers the confederation as one AS, and the confederation ID as the AS number. In the
above figure, AS 200 is the confederation ID.
Confederation has a deficiency. When you change an AS into a confederation, you must
reconfigure your routers, and the topology will be changed.
In large-scale BGP networks, both route reflector and confederation can be used.

MP-BGP

BGP-4 transmits IPv4 unicast routes, but does not transmit routing information of other network layer
protocols, such as IPv6.
To support more network layer protocols, IETF extended BGP-4 by introducing Multiprotocol Border
Gateway Protocol (MP-BGP). MP-BGP can transmit routing information of various network layer
protocols, for example, IPv4 multicasts, IPv6 unicasts, IPv6 multicasts, and VPNv4 routes.
Routers supporting MP-BGP can communicate with routers not supporting MP-BGP.
MP-BGP extended attributes
Prefixes and next hops are key routing information of network layer protocols. In BGP-4, each
update message can carry prefixes of feasible routes in the Network Layer Reachability Information
(NLRI) field, prefixes of unfeasible routes in the withdrawn routes field, and next hops in the
NEXT_HOP attribute. The NLRI field, withdrawn routes field, and NEXT_HOP attribute cannot be
extended to carry information of multiple network layer protocols.
To support multiple network layer protocols, MP-BGP defines the following path attributes:
•
MP_REACH_NLRI—Multiprotocol Reachable NLRI, for carrying prefixes of feasible routes and
next hops for multiple network layer protocols. Such routes can then be advertised.
•
MP_UNREACH_NLRI—Multiprotocol Unreachable NLRI, for carrying prefixes of unfeasible
routes for multiple network layer protocols. Such routes can then be withdrawn.
MP-BGP uses these attributes to advertise feasible and unfeasible routes of different network layer
protocols. BGP speakers not supporting MP-BGP ignore updates containing these attributes and do
not forward them to its peers.
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