I have reachability to a certain /25 prefix at two different sites. These sites advertise the /25 via EBGP into a L3 IPVPN (MPLS). I am AS-path prepending one of these sites' advertisements to make it a "backup" path for the /25. However, remote sites participating in this L3 IPVPN only ever learn one of the routes/paths via EBGP. How can I get both of these routes/paths installed into the routing tables of my remote sites?
I've performed a test where I advertise 188.8.131.52/32 from both of these sites, and get the same results. When I remove the advertisement from one of the sites, the route remains in the routing table. It only disappears from the remote site routing table when I stop advertising it from both sites. The duration of the route being learned doesn't change when one of the sites stops advertising, indicating that my provider seems to let the other site's advertisement come through.
These are Juniper devices running 12.1 code.