Hello
After several failed attempts, I finally have a Cisco ATA Box (SPA122) and a SNOM 370 (according to these instructions [www.swisscom.ch/de/privatkunden/hilfe/loesung/sip.html)](http://www.swisscom .ch/de/privatkunden/hilfe/loesung/sip.html)) successfully connected directly to the Internet Box Plus.
I have equipped both devices with a fixed IP address.
What also works is to operate the SIP devices behind a firewall.
rfaj