one way voice

[almatel]

hi all,
I have installed an OXE PBX in a company which has many branch offices in a different cities.each branch has a subnet different from others and the company policy is not allowed the branch offices to connect each other, the access and connect to the main Office is only allowed (vice versa ).
the access to the PBX CPU is allowed from any branch to the main office and .IP phone users in any branch can connect IP phone users in a main office and everything is ok (ip phones gets its ip from branch office subnet +pbx cpu ip@ as a tftp ip@ ).
the problem is occurs when IP phone users in any branch calls IP phone users in a other branch "one way voice".
is there any solution to solve this issue without Violation of the company policy.
attached is a simple example of the network topology .
BR

[sadim]

Hi,
The normal soluction needs that all branchs have local public network access and ddi's for the local users, then you can implement the hybrid media gateway.
You will configure a ip domain per branch, in those ip domains you will say that the number of call extra domain are 0 (no calls), and then implement the private to public overflow

Best Regards