Hi I have a Cisco Call Manager in the site A and a Cisco Call Manager Express in the side B, the phones of site A can make calls to phones in the site B, and the phones in the Site B can make calls to phones in the Site A. The problem is the conference, for example, the extension in the site A call to 3001 extension, the call is established, so the extension 3000 call to 3002 extension and is added to the conference. In the Site B, the extension 4000 call to 4001 extension and the call is established, so the extension 4000 call to extension 4002 and s added to the conference. BUT !!! When the extension 3000 (from the site A) call to extension 4000 (from the site B) the call is established, then the extension 3000 call to extension 4002 and the call is established, but when the 4002 extension is incorporated into the conference, the voice call end.

In summary, the voice conferences between the telephones from site A and site B are not established.