I have two Sonicwall TZ-105 with a site to site VPN between the two, however I'm having issues with the VOIP phone system. This happens for both sites: the phone rings and shows extension, but nothing is heard on either end. The tech with the VOIP system says ports are blocked. I don't believe they are between the site-to-site VPN. Is there away to debugging and/or test for ports that are open or blocked on this site-to-site VPN?