Not all leaf nodes can support label route or recursive opaque, so recursive opaque functionality can be transferred from the leaf to the ASBR, as shown in Figure: Optimized Option C — leaf router not responsible for recursive FEC.
In Figure: Optimized Option C — leaf router not responsible for recursive FEC, the root advertises its unicast routes to ASBR-3 using IGP, and the ASBR-3 advertises these routes to ASBR-1 using label-BGP. ASBR-1 can redistribute these routes to IGP with next-hop ASBR-1. The leaf resolves the actual root 10.0.0.14 using IGP and creates a type 1 opaque value <Root 10.0.0.14, Opaque <8193>> to ASBR-1. In addition, all P routers in AS 2 know how to resolve the actual root because of BGP-to-IGP redistribution within AS 2.
ASBR-1 attempts to resolve the 10.0.0.14 actual route via BGP, and creates a recursive type 7 opaque value <Root 10.0.0.2, Opaque <10.0.0.14, 8193>>.