ASA 5525 IPS and AnyConnect on Apple iOS13: IPSec VPN gets established but not traffic

[TobiasF25562]

Hi,

we have a ASA 5525 IPS, and can not use IPSec VPN connections with Apple Iphones that have the iOS13-Update (or 13.1) installed, using the AnyConnect Secure Mobility Client (4.8.00807).

The connection is established, but it's not receiving any data through the vpn tunnel.

There seems to be a related topic with "Libreswan IPSec server", where you have to specify "sha2-truncbug=no" in the config: https://forums.developer.apple.com/message/376572#376572

Is there any known solution to this issue? See attached screenshot of the iOS-Client "Statistics" page: 0 Frames ("Rahmen") received.

On iPad, iPad OS 13.1, same config, it is miraculously working.

Thank you very much in advance!

[TobiasF25562]

To whom it may concern: We've found out, that if we deactivate the "VoLTE" feature in our mobile Network settings, the AnyConnectClient works fine again.