firstly, we need to verify how many public ip in total.
assuming there is only one public ip, then you need to configure the speedtouch into bridging-mode instead of routing-mode; configure public ip on the pix and depends on the isp, configure pppoe as well.
assuming there are more than one public ips, then you can leave the speedtouch in routing-mode. if this is the case, you need at least 3 public ips; 2 for the speedtouch and 1 for the pix.
vpn pass-through refers to the ability to identify and forward vpn packets. with this enabled, host behind the speedtouch will be able to establish vpn. nonetheless, it doesn't matter if the speedtouch is running in bridging-mode.
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...