We've encountered this type of NAT issue with multiple PBX systems. The most reliable solution we've found for the array of PBX level problems is to put a small SBC at the site to handle NAT/media traversal and any header rewrites needed. A Cisco ISR router running CUBE or an Acme Packet SBC work fine, and I'm sure there are others out there that could be used as well. -- Jason Nesheim Manager, Network Architecture TelePacific Communications Office: 702-405-3571 Mobile: 702-885-0815 Fax: 702-724-2110 From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org] On Behalf Of Robert Dawson Sent: Tuesday, April 03, 2012 6:41 AM To: voiceops at voiceops.org Subject: [VoiceOps] Mitel 3300 - NAT - Media Issue Working with someone on SIP trunks for a Mitel 3300. The Mitel is sitting behind a NAT on a Cisco 3700 (i.e. no fixup/ALG) and inbound media is failing because the phones private IPs are being targeted directly in the SDP. Even if I force all media back to the NAT address it still fails because there is no translation for the phones. Anyone know if there is a way to force the Mitel to proxy the media or have any insight into getting around this shy of putting a proxy at the customer site(which is what we should probably do anyway)? Thanks, Rob