Connect 2 sip servers together. 1 asterisk , 1 foreign

How do I setup. To send calls from 1 sip server to asterisk.

The other sip server is connected to asterisk trough an extension. But when my extension makes the call. The extension number is showing up. How do you make the extension take the CID of the foreign sip server.

The calls goes trough fine, but its always, my extension number showing up.