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BGP Address Family Identifiers Technical Level

Address Family Identifier (AFI)

This field carries the identity of the Network Layer protocol associated with the Network Address that follows. Presently defined values for this field are specified in RFC 1700.

Address Family Numbers
Number Description
0 Reserved
1 IP (IP version 4)
2 IP6 (IP version 6)
4 HDLC (8-bit multidrop)
5 BBN 1822
6 802 (includes all 802 media plus Ethernet "canonical format")
7 E.163
8 E.164 (SMDS, Frame Relay, ATM)
9 F.69 (Telex)
10 X.121 (X.25, Frame Relay)
11 IPX
12 Appletalk
13 Decnet IV
14 Banyan Vines
65535 Reserved

Subsequent Address Family Identifier (SAFI)

This field provides additional information about the type of the Network Layer Reachability Information carried in the attribute.

The multiprotocol BGP (MBGP) feature adds capabilities to BGP to enable multicast routing policy throughout the Internet and to connect multicast topologies within and between BGP autonomous systems. In other words, multiprotocol BGP (MBGP) is an enhanced BGP that carries IP multicast routes. BGP carries two sets of routes, one set for unicast routing and one set for multicast routing. The routes associated with multicast routing are used by the Protocol Independent Multicast (PIM) to build data distribution trees.

The <AFI, SAFI> message must equal 32 bits

A BGP speaker that uses Multiprotocol Extensions should use the Capability Advertisement procedures [BGP-CAP] to determine whether the speaker could use Multiprotocol Extensions with a particular peer.

The fields in the Capabilities Optional Parameter are set as follows. The Capability Code field is set to 1 (which indicates Multiprotocol Extensions capabilities). The Capability Length field is set to 4.

The use and meaning of the Capabilities Optional Parameter field is as follow:

0       7      15      23      31
|      AFI      | Res.  | SAFI  |

         AFI  - Address Family Identifier (16 bit), encoded the same way as in the Multiprotocol Extensions

         Res. - Reserved (8 bit) field. Should be set to 0 by the sender and ignored by the receiver.

         SAFI - Subsequent Address Family Identifier (8 bit), encoded the same way as in the Multiprotocol Extensions.

A speaker that supports multiple <AFI, SAFI> tuples includes them as multiple Capabilities in the Capabilities Optional Parameter.

To have a bi-directional exchange of routing information for a particular <AFI, SAFI> between a pair of BGP speakers, each such speaker must advertise to the other (via the Capability Advertisement mechanism) the capability to support that particular <AFI, SAFI> routes.

Imported from Nokia support database

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