Hi Federico,
thank you for your response.
But ... it was my fault.
For debugging I commented 2 lines and forget to reenable them.
But the main problem is that when I come in with IPv6 and go out to an
IPv4 PBX,
it looks like I have to replace the contact header with a random IPv4
private address.
If in the contact header is still the IPv6 address, freeswitch will no
use the way back over the proxy.
But that's an other problem.
Best regards,
Bernd