Operation Manual – Routing Protocol
Quidway S5600 Series Ethernet Switches-Release 1510 Chapter 5 BGP Configuration
Huawei Technologies Proprietary
5-14
VI. Confederation
Confederation is another way to limit the number of IBGP connections in an AS. It
divides an AS into multiple sub-ASs. The IBGP peers in each sub-AS are fully
connected. The sub-ASs are connected through EBGP connections,
Figure 5-12
shows a confederation implementation.
EBGP
EBGP EBGP
IBGP
AS65001
AS65002
AS200
AS65003
AS100
IBGP
IBGP
Figure 5-12 A confederation implementation
To a BGP speaker that does not belong to any confederation, the sub-ASs of a
confederation are a whole, and the information about the sub-ASs is invisible to the
BGP speaker. The confederation ID, which is usually the corresponding AS number,
uniquely identifies a confederation. In
Figure 5-12, AS200 is a confederation ID.
The disadvantage of confederation is that when a AS changes from non-confederation
to confederation, configurations are needed on the routers, and the topology changes.
In a large-scale BGP network, router reflector and confederation can be used
simultaneously.
5.1.5 MP-BGP
I. MP-BGP overview
BGP-4 can only process IPv4 routing information. It is not applicable to the applications
using other network layer protocols (such as IPv6) when inter-AS routing information
exchange is required.
To support multiple network layer protocols, IETF extends BGP-4 to MP-BGP. MP-BGP
standard is described in RFC2858, multiprotocol extensions for BGP-4.a
MP-BGP is backward compatible. It enables communications to routers with BGP-4
employed.
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