Understanding the connection establishment issue between Grandstream GXW450x and IP PBX



GXW4501 is a digital VoIP gateway designed to connect digital T1/E1/PRI lines to an IP network, allowing businesses to take benefit of VoIP technology to reduce costs and improve efficiency. This article describes the connection issue between the gateway and IP PBX.


GXW4501 is connected with a traditional PBX via the E1 port from each device. It is found that the connection status shows ‘out of sync’ and fails.

Debug Logs

The debugging logs from GXW450X are required for analysis:

  • PRI Signaling Traces under GXW4501’s UI > Maintenance > Signaling Troubleshooting
  • Syslog under GXW4501’s UI > Maintenance > Syslog > PBX Modules
    – PBX (set to ALL)
    – chan_dadhi (set to ALL)
    – Save and Apply


Figure 1. The PRI traces shows that it receives ‘Got SABME from network peer’. Make sure that PRI_CPE is selected under Gateway Settings > Interface Settings > Basic Settings
Figure 2 Go to Dashboard > Interface Status > Digital to determine the error message. ‘Digital 1 Error Configured’ indicates the PRI signaling type is mismatched.