220.127.116.11 80.62.yyy.xxx (Traffic source IP: 18.104.22.168 - when it should see 22.214.171.124)
The above is meant to show that I have an ASA5510 that is configured with an L2L tunnel with peer 126.96.36.199.
The ISP of 188.8.131.52 is somehow not doing its routing/translating correctly as the source IP of traffic originating from my ASA5505 is another than the one configured on the ASA5505. This is only the case when talking about ESP traffic. UDP (ISAKMP) traffic is correct.
The VPN tunnel is successfully established (both phase 1 and 2), but no traffic can traverse the tunnel. It has been working fine untill this morning.
Not long ago ISAKMP traffic was translated the same way as ESP traffic - it was working then, as long as the non-NAT'ed device initiated the tunnel.
I hope I have explained myself, so that you can understand it