To better answer your question can you explain the network topology?

Are the sites with Stratanet connected via a WAN or VPN? What type of circuit?

Do remote users have access to the LAN on either site via a hardware based or software based VPN?

Is this a new design/sale or an addition to an already existing system?

While Toshiba IP phones can operate behind NAT, the xIPU card cannot. This is, potentially, your hurdle and depending on the above determines how many xIPU cards are needed.

You MIGHT be able to give the MIPU card a static public IP and pull this off. We have an account where we use 1 MIPU card and they have internal IP phones and external IP phones and, with everything registered to the MIPU, all works. I believe that for this to work BOTH MIPU cards on either side will need a public static IP so the SN can work. The IPTs will probably be behind some type of firewall but they should be able to register to the public IP of the MIPU from behind NAT.

This should work but ignores all network security so it is not recommended. Not to say it isn't done, just not advised.

IF this is a new sale/design and no contracts have been signed, you should take a good look at the IPEdge which is designed to sit behind a firewall and benefit from the protection. You still need a public static IP which you define in the IP Edge server which is then able to perform NAT traversal. We have utilized this and, compared to the CIX it is a much easier implementation and far more secure. ~ Mike

Michael Meyer