Hello @NDP ,
in multiprotocol BGP an address family specifies a type of NLRI
Example : Ipv4
A sub address family SAFI specifies some more specific attributes
Example:
IPv4 unicast
IPv4 multicast
IPv4 unicast and multicast
AN NLRI with AFI IPv4 subAFI unicast specifies a prefix for Unicast routing only.
An NLRI with AFI IPv4 subAFI multicast specifies a prefix for the only purpose of passing a multicast RPF check in inter AS multicast
An NLRI with AFI IPv4 subAFI unicast and multicast does both of the above
Other important examples are the various flavors of VPLS:
VPLS LDP based with MP BGP discovery uses an AFI and a specific sub AFI
VPLS BGP based with MP BGP discovery uses the same AFI but a different sub AFI .
to be noted the prefix lengths of these two are different 96 bits and 137 bits respectively
Hope to help
Giuseppe
