Carrier authentication

Carrier authentication controls how each side decides that SIP traffic is trusted.

List your current carriers

sipsandwich represents each connected carrier or PBX as a SIP provider trunk. To see the carriers already configured on your account, open SIP Providers at https://app.sipsandwich.ai/app/trunks.

For API automation, list the same tenant-scoped carrier connections with GET /api/v1/sip/trunks and a tenant API token:

curl https://api.sipsandwich.ai/api/v1/sip/trunks \
  -H "Authorization: Bearer $SIPSWICH_API_TOKEN"

The response's trunks array contains the existing SIP provider trunks. See List SIP provider trunks for the complete response contract.

IP authentication

Use IP authentication when the carrier identifies customers by network address rather than a SIP login.

You give the carrier the sipsandwich edge IP addresses that may send traffic. The carrier gives you the source IP addresses or CIDR ranges that sipsandwich should accept.

You do not need a SIP authentication username or password.

Registration

Use registration when the carrier expects a device or platform to stay signed in. sipsandwich periodically sends REGISTER requests with the username and password supplied by the carrier.

Registration is common for PBX trunks and providers that model the connection like a continuously signed-in SIP endpoint.

SIP digest

Use SIP digest when the carrier accepts an initial call request, challenges it with 401 Unauthorized or 407 Proxy Authentication Required, and expects the request to be retried with credentials.

Digest authentication uses a username and password but does not require an active registration session.

Information to collect

Access model	Required from your carrier
IP authentication	SIP host, port, transport, and source IP/CIDR allowlist
Registration	Registrar host, port, transport, username, password, and optional outbound proxy
SIP digest	SIP host, port, transport, authentication username, password, and optional realm