Saturday, August 8, 2015

BGP4 AFI/SAFI Numbers and Captures of BGP Updates

Below are the BGP4 AFI/SAFI numbers. Also there are lots of SAFI numbers but these are the commonly used ones.
  • IPv4 (AFI/SAFI 1/1)
  • VPNv4 (AFI/SAFI 1/128)
  • VPNv6 with v4-mapped nhops (AFI/SAFI 2/128)
  • 6PE with v4-mapped nhops (AFI/SAFI 2/4)

So, how this information is useful? 


When you configure MP-BGP (means that you configure BGP to carry network layer reachability information for address families other than unicast IPv4) BGP installs the MP-BGP routes into different routing tables. Each routing table is identified by the AFI and a SAFI).

SAFI field value

Description

Reference

1

NLRI used for unicast forwarding.

RFC 2858

2

NLRI used for multicast forwarding.

RFC 2858

3

NLRI used for both unicast and multicast forwarding.

RFC 2858

4

NLRI with MPLS labels.

RFC 3107

64

Tunnel SAFI.

draft-nalawade-kapoor-tunnel-
safi -01.txt

65

Virtual Private LAN Service (VPLS).


66

BGP MDT SAFI

draft-nalawade-idr-mdt-safi-00.txt

128

MPLS-labeled VPN address

RFC-ietf-l3vpn-rfc2547bis-03.txt



Below are the wireshark captures of the bgp updates messages of different AFI/SAFI.

IPv4 EXAMPLE (AFI/SAFI 1/1) 

IPV4


























6PE EXAMPLE (AFI/SAFI 2/4)

You can see the AFI/SAFI numbers, NLRI prefix-label information, and next-hop information inside of the MP_REACH_NLRI attribute.

IPV6





VPNv4 EXAMPLE (AFI/SAFI 1/128)


VPNV4





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