When a new SIP call arrives at Enswitch, it needs to decide whether:

• The call is from a local user. If so it should be authenticated, and then allowed to call any number its class of service allows.
• The call is from an external system. If so it should not be authenticated, but then must not be allowed to make chargeable calls unless forwarded by a customer's settings.

To do this, Enswitch looks at the domain in the From: SIP header. If the domain is one that it considers local, it assumed to be from a local user, else it is assumed to be from an external system.

To add a new domain

1. Log in to the Enswitch web interface.
2. Go to System » Domains.
3. Click the "New" button.
4. Enter the domain name and optionally a description.
5. Click the "Save" button.
6. Update your DNS server to send calls to this domain to the system. If you have an Enswitch cluster with multiple machines, use the OpenSIPS service address. You can use SRV records if you wish.