I have a router that takes a long time to converge after reboot. To fix
that I do not want to advertise my prefixes until the router is fully
ready. But I still want to establish the BGP sessions otherwise the router
will never be ready. So we program in a delay until advertising after BGP
Now if my peers automatically converted BGP announced prefixes into ACLs,
they would blackhole any traffic that might come to this router during
startup. This is obviously not good.
BGP announced prefixes tells you what I can receive but not what I can
send. Interpreting that any other way is abusing the protocol. You would
need a new BGP extension so we could announce what we might send
independent of what we want to receive.
IRR generated ACL filters might work if agreeable by the peer.