VoIP glossary
What is IP authentication?
IP authentication is a way of securing a SIP trunk where the provider accepts calls only from a list of approved public IP addresses, with no username or password.
IP authentication explained
It is the usual choice for servers with a fixed public IP, such as a PBX in a data centre or a softswitch. Setup is simple and there are no credentials to steal. The trade-off is that you must tell the provider whenever your IP changes, and it does not suit offices with dynamic addresses.
The alternative is digest (register) authentication, where the PBX logs in with a username and password. Some deployments combine both, allowing only known IPs and also requiring credentials, for an extra layer of protection against toll fraud.
Example
A company’s Asterisk server at 203.0.113.25 is added to the trunk’s allow-list. Calls from that address are accepted; an INVITE from any other IP gets a 403 Forbidden.
Put it into practice
Prepaid SIP trunks and wholesale routes from $200. Ask sales for rates or the NOC for a technical answer.