Blog PostAsterisk is not easy to trouble shoot

I have setup Asterisk PBX, everything works perfectly, with one SIP trunk, however, when I try to add the second trunk, it just doesn't register to any of them. When I read the logs, I see that it times out while registering... So, I run tcpdump and try to see what's going on... From what I have seen is that it sends the register command to the SIP server, however, the SIP server replies back saying:

SIP/2.0 401 Unauthorized - no credentials are provided

Now, I am researching this issue, I hope I can fix this soon.