we have recently deployed a TMG 2010 server in our network.We have configured it for VOIP by using Configure VOIP option in TMG but it is not working.We are using Vonage box for VOIP.It is connected to our core switch that is connected to TMG and then Router i.e
Vonage Box->Cisco 3560 Switch -> TMG -> Cisco 1801 Router
The Data traffic and internet is working for internal PCs connected to core switch.
I have configured VOIP by selecting "IP phones are connected directly to external hosted IP PBX" and provided External and internal in subsequent screens for configuring "External IP PBX server" and "Internal SIP Phone Network Addresses" respectively.But it is not working and vonage is displaying "Check if ur Internet is down".However internet is working on PCs.
Plz guide me where am I wrong or how to configure TMG to allow Vonage VOIP.