The SIP gateway will not accept INVITE requests destined for an IP address that does not exist on the gateway. The NAT device would have to do a SIP "fixup" to translate the IP addresses in the SIP messages. Cisco PIX firewalls support this with version 6.2 and above. It is SIP authentication problems. Can you send me the output of "debug ccsip all"
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...