BGP Protocol : iBGP vs MP-iBGP protocol

👉What is BGP protocol ?

BGP (Border Gateway Protocol) is a routing protocol used on the Internet and in large enterprise networks to exchange routing information between different networks, known as autonomous systems (AS). BGP is the protocol that enables the Internet to function as a network of networks, allowing data to be transmitted from one AS to another.

BGP is a path-vector protocol, which means that it selects the best path for data to take based on a variety of factors, including the number of autonomous systems the data must traverse, the network policies of the AS, and the quality and availability of the links between the AS. BGP is able to route data over multiple paths and select the optimal path based on its routing policy.

Fig 1.1- BGP Protocol : iBGP vs MP-iBGP protocol

👉What is the difference between iBGP vs MP-iBGP ?

iBGP protocol: iBGP is a protocol that allows BGP routers within the same autonomous system to communicate routing information (AS). Since it is used within an AS and does not communicate routing information with routers outside the AS, it is classified as an internal routing protocol. 

iBGP is used to disseminate external routing information obtained from other autonomous systems to all routers within the same autonomous system, as well as to verify that all routers within the AS have consistent routing information.

MP-IBGP protocol: MP-IBGP is an iBGP variation that allows different address families or network layer protocols, such as IPv4 and IPv6, to communicate routing information. Several address families may be transported over the same BGP session using MP-IBGP, which simplifies BGP routing configuration and administration.

Originally, BGP only supported IPv4 unicast prefixes. It was later extended to support other protocols such as IPv4 multicast, VPNv4 (for MPLS VPN) and IPv6.This extension is referred to as Multiprotocol BGP (or MP-BGP)

Multiprotocol BGP allows information about the topology of IP Multicast-capable routers to be exchanged separately from the topology of normal IPv4 unicast routers. Thus, it allows a multicast routing topology different from the unicast routing topology. Although MBGP enables the exchange of inter-domain multicast routing information, other protocols such as the Protocol Independent Multicast family are needed to build trees and forward multicast traffic.

Multiprotocol BGP is also widely deployed in case of MPLS L3 VPN, to exchange VPN labels learned for the routes from the customer sites over the MPLS network, in order to distinguish between different customer sites when the traffic from the other customer sites comes to the PE router for routing.

Fig 1.1-iBGP vs MP-iBGP protocol

Conclusion
In conclusion, MP-IBGP is used to share routing information for different address families, whereas iBGP is used to transmit routing information inside a single AS. 

In essence, MP-IBGP is an extension of iBGP that allows for the transmission of several forms of routing information during the course of a single BGP session.

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