BGP Address Families

Back in 2007, RFC 4760 defined extensions to BGP to make it capable of carrying more than IP traffic, at one time. This is MP-BGP, or Multiprotocol BGP.

Each type of traffic that BGP can carry is an address family. Address families include:

  • IPv4 and IPv6 – Including unicast and multicast routes
  • L2VPN – layer-2 VPN information, such as VPLS or EVPN
  • VPNv4 and VPNv6 – Layer-3 VPN information. This is MPLS VPN
  • EVPN - for VxLAN overlay.

By default on Cisco devices IPv4 is the default address family and some configuration like neighbor activate, soft configuration and network statements etc are nested below the IPv4 address family. However if you enter the no bgp default ipv4-unicast command in the BGP configuration, you will prevent BGP from automatically assigning each newly defined neighbor into address-family ipv4 section. Having a strict per address-family configuration is the recommended method for all new deployments.


Juniper has a number of address-family extensions listed below. Source: Juniper

Unicast IPv4—If you do not explicitly specify the address family, the router is configured to exchange unicast IPv4 addresses by default. You can also configure the router to exchange unicast IPv4 routes in a specified VRF.

Multicast IPv4—If you specify the multicast IPv4 address family, you can use BGP to exchange routing information about how to reach a multicast source instead of a unicast destination. For information about BGP multicasting commands, For a general description of IPv4 multicasting, see IPv4 Multicast Overview in the JunosE Multicast Routing Configuration Guide.

VPN IPv4—If you specify the VPN-IPv4 (also known as VPNv4) address family, you can configure the router to provide IPv4 VPN services over an MPLS backbone. These VPNs are often referred to as BGP/MPLS VPNs.

Unicast IPv6—If you specify the IPv6 unicast address family, you can configure the router to exchange unicast IPv6 routes or unicast IPv6 routes in a specified VRF. For a description of IPv6, see IPv6 Overview in the JunosE IP, IPv6, and IGP Configuration Guide.

Multicast IPv6—If you specify the multicast IPv6 address family, you can use BGP to exchange routing information about how to reach an IPv6 multicast source instead of an IPv6 unicast destination. For a general description of IPv6 multicasting, see IPv6 Multicast Overview in the JunosE Multicast Routing Configuration Guide.

VPN IPv6—If you specify the VPN-IPv6 address family, you can configure the router to provide IPv6 VPN services over an MPLS backbone. These VPNs are often referred to as BGP/MPLS VPNs.

L2VPN—If you specify the L2VPN address family, you can configure the PE router for VPLS L2VPNs or VPWS L2VPNs to exchange layer 2 network layer reachability information (NLRI) for all VPLS or VPWS instances. Optionally, you can use the signaling keyword with the address-family command for the L2VPN address family to specify BGP signaling of L2VPN reachability information. Currently, you can omit the signaling keyword with no adverse effects.

Route-target—If you specify the route-target address family, you can configure the router to exchange route-target membership information to limit the number of routes redistributed among members. For a description of route-target filtering, see Understanding Route-Target Filtering for MBGP VPNs Overview.

VPLS—If you specify the VPLS address family, you can configure the router to exchange layer 2 NLRI for a specified VPLS instance.

VPWS—If you specify the VPWS address family, you can configure the PE router to exchange layer 2 NLRI for a specified VPWS instance.

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