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)

IPv6 Subnet Calculation

IPv6 address formatting is sometimes very difficult. But website www.dnskey.net is making it easier. There are lots of web pages but this one is the simplest and very fast. If you want to divide your /32 subnet to /35s just write your prefix and submit!

Below is the output of /32 prefix divided into /35 subnets.

------------------------------------------------------
Prefix entered  => 2001:0DB8::/32 
Correct /32 prefix =>      2001:0DB8:0000:0000:/32
Subnet mask            =>      FFFF:FFFF:0000:0000:
You want /35 from =>      2001:0DB8:0000:0000:/32
Number of /35 subnets =>   8 
------------------------------------------------------
/35 prefixes 
------------------------------------------------------
2001:0DB8:0000:0000::/35  
2001:0DB8:2000:0000::/35  
2001:0DB8:4000:0000::/35  
2001:0DB8:6000:0000::/35  
2001:0DB8:8000:0000::/35  
2001:0DB8:A000:0000::/35  
2001:0DB8:C000:0000::/35  
2001:0DB8:E000:0000::/35