http://cs.i2p/blog/ipv6
In our implementation, a single IPv6 address (per server) will act as the entry point, and another single address acts as the exit (the one the internet sees you as having). The IPv6 address space is very large, and most of our servers have an entire /64 subnet (2 64 [18,446,744,073,709,551,616] addresses), more than enough for each client, but we decided against assigning individual IPs to each client because that could introduce correlation...