To send announces with VLC, you need to use the complex syntax of VLC's stream output, like this:
% vlc -vvv input_stream --sout '#standard{access=udp,url=239.255.12.42,sap="Test Stream"}' --ttl 12 |
where video1.xyz is the file you want to stream, 239.255.12.42 is the multicast IP address you want to stream on, Test Stream is the name that will be used for this program in the SAP announces and 12 is the value of the TTL (Time To Live) of the stream and of the SAP announces.
To do the SAP announces in IPv6, just add the sap_ipv=6 option:
% vlc -vvv input_stream --sout '#standard{access=udp,url=239.255.12.42,sap="Test Stream",sap_ipv=6}' --ttl 12 |