We have a Lync 2013 internal setup with 2 FE servers, DNS load balanced, an edge pool with one Edge server, and a Reverse Proxy (TMG2010). Internally we can have meetings with no issue. Users join the meeting with audio and video. However, if internal users try to join a meeting from another company, they get kicked out as soon as they try to use Audio or Video. They can IM only. If I connect from home on my work laptop, using Lync Full client, I am able to connect and use Audio and Video. We have open federation enabled through the edge and I have the AV Edge set as NATTed. We have verified the DNS records and have even gone as far as opening the internal and external firewalls wide open (just to test) and it has no effect. This affects all internal clients regardless of location (we have multiple sites, all use same Lync FE pool.) Has anyone seen behavior like this?