Registered AOR Mode for softphone behind NAT - inbound calls not working

Yeti-Switch
1

Hello,

We are running Yeti Switch v1.13 on GCP and trying to terminate
inbound calls directly to a softphone (Zoiper) with dynamic IP
behind NAT, without an intermediate PBX.

Our setup:

  • Carrier (Tlcom) → Yeti SEMS → softphone (Zoiper)
  • Gateway configured with Registered AOR Mode: “Use AOR as is”
  • Incoming Auth Username/Password configured on the gateway
  • Zoiper registers successfully - we can see the AOR in
    registrar.show.aors with correct Contact including IP and port

The problem:
When an inbound call arrives, SEMS sends the INVITE to the
correct IP from the AOR, but uses the PORT from the Gateway
configuration instead of the port from the registered Contact.

Example:

  • AOR Contact: sip:user@203.x.x.x:54604
  • Gateway Port: 5060
  • SEMS sends INVITE to: sip:number@203.x.x.x:5060 (wrong port)

The correct port from the AOR is never used. This causes the
INVITE to be dropped by the NAT since the softphone is not
listening on port 5060 externally.

Questions:

  1. Is Registered AOR Mode designed to work with softphones
    behind NAT, or only for SIP trunks with semi-static IPs?
  2. Is there additional configuration in sems.conf required
    to make SEMS use the full Contact URI (including port)
    from the registration?
  3. Has anyone successfully terminated inbound calls to a
    mobile softphone using only Yeti/SEMS without an
    intermediate PBX?

Thank you

2

Is Registered AOR Mode designed to work with softphones
behind NAT, or only for SIP trunks with semi-static IPs?

yes, it works with softphones behind NAT too . But it designed to work with loadbalancer, so you have to configure it. We recommend to use kamailio or opensips for it. There are requirements for load balancer: Load balancer | Yeti Switch

Is there additional configuration in sems.conf required
to make SEMS use the full Contact URI (including port)
from the registration

No any additional configuration in sems.conf required

Has anyone successfully terminated inbound calls to a
mobile softphone using only Yeti/SEMS without an
intermediate PBX?

Yes. Lots of our customers doing this.

3

It is hard to troubleshoot your case without trace. Could you provide pcap trace for registration and call?