Editing Border Gateway Protocol (section)

== Extensions ==
Multiprotocol Extensions for BGP (MBGP), sometimes referred to as Multiprotocol BGP or Multicast BGP and defined in {{IETF RFC|4760}}, is an extension to BGP that allows different types of addresses (known as address families) to be distributed in parallel. Whereas standard BGP supports only IPv4 unicast addresses, Multiprotocol BGP supports IPv4 and IPv6 addresses and it supports unicast and multicast variants of each. 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 [[provider edge router]] for routing.

Another extension to BGP is [[multipath routing]]<!--or is it [[Equal-cost multi-path routing]]?-->. This typically requires identical MED, weight, origin, and AS-path although some implementations provide the ability to relax the AS-path checking to only expect an equal path length rather than the actual AS numbers in the path being expected to match too. This can then be extended further with features like Cisco's dmzlink-bw which enables a ratio of traffic sharing based on bandwidth values configured on individual links.