There are 2^128 IPv6 addresses. The number of "gargantuan blocks" possible with that many addresses is quite large. The problem of routing the allocated blocks

There are 2^128 IPv6 addresses. The number of "gargantuan blocks" possible with that many addresses is quite large. The problem of routing the allocated blocks is solved incrementally as needed by network expansion. In the event we need to route more than we can now routers are upgraded or topologies are changed.