I had implemented voip (inter cluster trunk) with 3 remote sites (1 to US, 2 to China)for over 2 years. They are running fine. I had problem on the fouth new sites (the configuration in call manager are identical except change the remote call manager address. The new site in China can call run voip to Singapore but Singapore can not call the new China site. The connection between Singapore and new China site is on mpls line and no problem on normal data traffice. I did delete the voip/trunk configuration and re-created the configuration in the two locations but I am having the same problem (Singapore can not make voip call to China). In Singapore CDR, it shows the voip call uses the correct css, trunk (remote call manager ip address). Would someone give me some insight on how to find the root cause and make this new site voip works with both direction.