ip protocol 50, esp. maybe ip protocol 51, ah (not likely).
you may need udp 4500 or 10000 depending on whether it is using nat encapsulation (it probably is out of the box, but depends on what kind of a device it is connecting to). your best bet is to parse the pix logs from that ip to see what ports it is using
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...