Normally if you want to advertise a non existent route in the Cisco world, you’d need to create a null route to make that happen. I stumbled across the following post though when I was trying to suss out how to do the same in PAN-OS. In my case I wanted to advertise a GlobalProtect IP pool prefix across an AWS VPN using BGP.
Turns out you can quite simply directly add the prefix into the redistribute rule.
To check that your BGP config is working as required. Just simply check the RIB out table in the BGP runtime stats.
Thanks to Rtoodtoo (Great handle) where I found the info.