[Case Show] Abnormal Calls Due to Voice IP Address Conflict

Fault Description
During call setup, after a user connecting to an optical network unit (ONU) dials a number, the user hears busy tones; when the user is called, the phone of this user does not ring. During a call, the voice service is interrupted.

Alarm Information
Alarms frequently occur on ONUs, indicating that the H.248 interface is disconnected.

Possible Cause
-The ONU is faulty.
-The configuration of the ONU is incorrect.

Procedure
1. Use the inband network management IP address to log in to the ONU and query ONU alarms. It is found that the ONU periodically reports H.248 interface disconnection alarms. In addition, the interruption duration is basically the same. Therefore, the ONU is functional.
2. Ping the gateway of the voice IP address of the ONU from the ONU and send 1000 ping packets consecutively. It is found that packet loss occurs regularly.
3. Run the display interface vlanif command to query the MAC address of the ONU. Then log in to the gateway of the ONU and determine the relationship between the MAC address and the voice IP address of the ONU. After multiple queries, it is found that a voice IP address corresponds to two MAC addresses in different period of time. The voice IP address of an ONU is the same as the MAC address of the inband network management IP address. Therefore, users can query the relationship between the two MAC addresses and the inband network management IP addresses on the optical line terminal (OLT). Then the users can determine the network management IP addresses of the two ONUs.
4. Log in to the ONU, and run the display ip address command in voice over IP (VoIP) mode to check the voice IP addresses of the ONUs. It is found that the two ONUs have the same voice IP address.
5. Change the voice IP addresses of the two ONUs to be different. The fault is rectified.

Suggestion and Summary
Normally, abnormal voice service due to voice IP address conflict is caused by incorrect data configuration in commissioning during device deployment. In addition, the fault occurs on two adjacent devices with the same IP address. Therefore, R&D engineers are advised to check device configuration according to data plan in commissioning during device deployment to prevent this fault from occurring.