In one embodiment, a first router attaches to an attachment router based on detecting a first router advertisement message specifying an attachment prefix and a first tree information option. The first tree information option includes a first IP host address of a first clusterhead having established a first tree topology. The first router receives a second advertisement from a second router specifying a second address prefix, distinct from the attachment prefix and the first address prefix of the first router, and a second tree information option specifying a second IP host address of a second clusterhead having established a second distinct tree topology. If the first and second routers are at equal depths relative to the respective first and second clusterheads, routing information is shared, including first address prefix reachable via the first router, and a host route for reaching the first IP host address via the first router.