RFC 4760 Multiprotocol Extensions for BGP-4 January 2007
RFC 4760.
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 Capability Value field is defined as:
The Capability Value field is defined as:
0 7 15 23 31
+-------+-------+-------+-------+
| AFI | Res. | SAFI |
+-------+-------+-------+-------+
The use and meaning of this field is as follow:
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.
Note that not setting the field value to 0 may create issues
for a receiver not ignoring the field. In addition, this
definition is problematic if it is ever attempted to redefine
the field.
SAFI - Subsequent Address Family Identifier (8 bit), encoded the
same way as in the Multiprotocol Extensions.
A speaker that supports multiple
tuples includes them as
multiple Capabilities in the Capabilities Optional Parameter.
To have a bi-directional exchange of routing information for a
particular 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
route.