Wildix Common Issues

Occasional call setup failure or call drop

When Wildix systems receive SIP signaling to place a call on hold (a common scenario prior to call transfers), they may reply with a SIP 488 error message if the SDP contains both a null address ( and an offer/answer media attribute (e.g. a=inactive). This can cause unpredictable behavior in some endpoints.

The workaround is to enable "Support Refer and Hold" in the SIP trunk settings on your Wildix system:

Wildix Refer and Hold Support Configuration

Occasional outbound call drop

Wildix systems configured to use UDP as their transport protocol may experience outbound call failures if their packets exceed 1300 bytes and they switch to TCP as a transport protocol to support fragmentation. While technically within specification, an interoperability issue currently exists between Wildix and Clearfly that prevents a clean transport upgrade. Until the issue is resolved, Clearfly recommends decreasing the size of the INVITE packets that cause the transport change by minimizing codec support.

The preferred workaround is to change signaling transport protocols from UDP to TCP. If you do this, you'll also want to ensure that the Rport setting is set to REGISTER,INVITE at the same time:

Wildix Transport Configuration

Alternatively, Clearfly doesn't support G.711a-law, so simply disabling this codec should be a good workaround for some cases. For best results, we recommend disabling G.729, also.

Note: Ensure that ulaw remains checked, as Clearfly requires G.711u-law support for all phone systems:

Wildix Codec Configuration