https://www.cisco.com/c/en/us/support/docs/wireless/pgw-packet-data-network-gateway/218323-troubleshoot-blank-natted-ip-issue-in.html
Troubleshoot "Blank Natted IP" Issue in Event Data Record - Cisco
This document describes how to troubleshoot the 'blank natted IP' issue in the Event Data Record (EDR).
event datatroubleshootblanknattedip