Network Set up FOr Voip

Hello all

I have some issues. I have set up a network in my building with multiple segments. I have one main router for the building which contorls the traffric for the entire building. Then I have each office segments of he building with diffrent router. So office A which has it own router will connect to the main router of the building to connect to the internet. My main problem come with the SIP registration. MY peers under the segment lose registration from the servre.

Here is a breack down.

The main router which does not give DHCP. We only give static IPS is 192.168.17.1. From there office routers are given the IP of 192.168.17.X. In the sub network of each office we give 192.168.1.X. with DHCP.  


Now if I hook up a SIP phone to the suboffice network 192.168.1.X it loses registratioan withthe sip server after some time. I think I have a natting issue. How can I set this up correctly.