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) 

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.

VPNv4 EXAMPLE (AFI/SAFI 1/128)