Mike asked, "But how do we do that?"
using Wireshark. Filter tftp or udp.port eq 69 . Look for: cisco ip phone downloading xmldefault cnf xml repack
Specifically, a is a pre-configured, generic configuration file that has been stripped of proprietary CUCM dependencies so it can work with open-source PBXs (Asterisk, FreeSWITCH, 3CX) or standalone TFTP servers. Mike asked, "But how do we do that