My problem occurs also without any encryption. I'm connected to the internet and send a ping to the outside interface of the PIX. First a thought it is a problem with the router from the ISP, but we have also a CISCO 1605 connected to the same ISP router and there the ping work realy fine until 1472 bytes the I get the message fragmentition needed.
If I'm connected via the VPN Client 3.51 and send a ping to inside, I get the same results, but additional on the PIX, if debug ipsec is on, a message like this: IPSEC(ipsec_cipher_handler): ERR: bad pkt 10.1.80.3->10.1.1.1
I searched in the errordecoder from Cisco, but there are no results.
By the way, the pre-fragmentation is by default on and I didn't switch it off. It occurs not in IPSEC transfermode, which I'm 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...