I’m using AnyConnect both on iOS and OS X, you can read previously posted article on my blog: anyconnect, openconnect, ocserv. You can find ipv6-network and ipv6-prefix in ocserv’s sample.config:
# The IPv6 subnet that leases will be given from.
#ipv6-network = fc00::
#ipv6-prefix = 16
which means ocserv should be compatible with IPv6. And, in AnyConnect for iOS, ipv6 can be found somewhere, seems ipv6 is also compatible here. […]