Debug registration attempts and failures

running voiceaxis software and asterisk 1.4, trying to troubleshoot a loss in registration for an ATA. Interested in looking at registration rejections in general, but need to know for the ATA at the moment.

I have looked at the sip messages back and forth, the tcpdump from our feature servers, and a pcap from the remote edgemarc router…

how can i do it from the cli of the feature server where the registration attempts are taking place?