Versions: U1911 V2R3C50SPC300; IP Phone V2R3.
Networking: The U1911 connects to the PSTN through the SIP trunk. The IP phone and U1911 are deployed in the same network segment.
Fault symptom: When an IP phone dials the emergency number 112, the user hears a message saying that the call cannot be connected.
1. Check whether any configuration is missing on the U1911. The emergency call source, call prefix, and reanalysis are all defined.
2. Perform debug tracing on the U1911. It is found that the IP phone does not carry ACCESS-DOMAIN.
3. Update the IP phone configuration file by adding the access domain.
4. The test still fails. Packet capture on the U1911 finds that the U1911 returns "403 Forbidden".
5. Check the U1911 configuration again. It is found that the U1911 activates the heartbeat detection on the virtual trunk. Disable heartbeat detection and make a call again. The call is normal.