Problem: One Way Voice
It is possible for a call to be established but the voice path to be not present. This may be due to a problem with signaling or the route taken by voice packets (see No Voice Path for more details).
Other causes of one-way voice can include DSP hardware faults or DSP software "hanging".
Impact
No voice path is present in one direction.
Resolution
If the problem appears to be associated with all calls going through a specific route or router then it is likely to be associated with a router problem, a firewall blocking voice packets or NATs. Check the Call Manager/ Gatekeeper/ SIP Proxy for indications of signaling problems. Use traceroute or ping from each endpoint to verify the packet path. Use a VoIP network analyzer to decode signaling and investigate problem.
If the problem appears to be associated with a specific port, device or a TDM trunk interface on a gateway then it is likely to be related to the DSP. Check the DSP status for the specific Gateway to verify correct operation.
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