I am currently having an issue with a SA520 allowing VPN passthrough to a UC520 with the Cisco VPN 5.0 client. The tunnel is established however you can not ping any devices behind the UC520 or the UC520 itself for that matter. I get a reply from the UC520 IP saying destination host unreachable. Now, yesterday I was able to establish the connection and connect to the UC with the SA in front of it but today I could not connect at all. If we remove the SA520 the VPN is established and you can ping the default gateway without any issues.