The call history page has some bugs. It will do unexpected truncation when the string is too long. So I cannot use that page to find the IP of incoming calls.
Plus, most of the time, the call history page will NOT display the IP address at all.
I think I may have to use WireShark to directly examine the raw network traffic.
I will not even trust Syslog, as I suspect it may have the same string length limitation bug, and will only spit out incomplete/truncated log data.