Configuring a SIP gateway allows you to connect with outside carriers or other SIP machines. You can connect with other FreeSWITCH or Asterisk boxes, or to upstream carrier SIP trunks.
SIP gateways have many, many options—too many to list here, so we'll review just a few.
First you'll need to gather some information about the remote server to which you are connecting. The list generally includes:
You'll also need to know the phone number format your carrier expects when you send calls to ...