I have two sites that are connected via 8 bonded pairs of SHDSL on two Zhone EtherXtend 3384's in a bookend configuration. One side is the CO or central office, the other is just our main office. The CO side has our Metaswitch VP2510 (Class 4/5 Softswitch) and a Cisco 3845 router, the office has a Cisco 2851 router with an extremely long access list, and houses our corporate/public network. In an attempt to allow the router at the office to simply route traffic I recently put a Cisco ASA 5510 in front of our router at the office as a transparent firewall and set it to pass all traffic from the outside interface inwards. Before I put the firewall in place I had no problems whatsoever passing SIP traffic through our ACL to my Linksys 942 IP phones from the Metaswitch, All calls worked fine. I did not make any changes at all to our ACL on the router at the office, simply have put the firewall in place in front of the router and set to pass all traffic. Everything appears to work correctly, I have not had any complaints as far as any services being down except now I only get one way audio on my voip calls. I can make a call from my ip phone, it connects, I can hear audio from the other party but the person on the far end has no audio at all. I am not at the office right now to post my config of the ASA which I will do tomorrow but does anyone have any ideas of what could be happening or any suggestions? To verify the ASA is the problem I could take it back out of the loop but I would have to do it during our service window but I really need to find the actual problem.