I'm looking for the solution that will advertise aggregate and more-specific prefixes.
R1 (AS100) advertises 172.16.0.0/23 -> ISP1 AS200 (primary link)
R2 (AS100) advertises 172.16.0.0/23 -> ISP2 AS300 (secondary link)
Now I'd like to advertise 172.16.1.0/24 so it uses R2 as ingress/egress point for all traffic as primary link and still use the /23 aggregate.
Please let me know if you need more info.