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:
IP address or hostname of the server you are connecting to
Username and password (if any)
How the carrier/gateway expects Caller ID to be handled (which SIP header Caller ID should be placed in)
Whether registration is required
You'll also need to know the phone number format your carrier expects when you send calls to them, and how they'll send calls to you.
Finally, you'll need to decide which of your existing SIP interfaces to tie this gateway to. All gateways must be associated with a SIP interface (port and IP address). Note that, in most cases, a gateway can...