So why do I receive icmp response on sip register request. If ser built properly the myself value it should know that "new" myselfxxx.xxx.xxx.xxxx:5066 and to take care or requests he receives on port 5066 on sip level

Two questions: 1. Are the ICMP responses generated by requests destined to port 5066? 2. Did you set the port directive accordingly in ser.cfg?

Franz