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DSP Allocation Issues

Please assist,

My voice gateway (Cisco 3945) shows "19 DSP resource allocation failure" when running the command: show voice dsp group all.

sh inventory shows output below:

NAME: "PVDM3 DSP DIMM with 32 Channels on Slot 0 SubSlot 3", DESCR: "PVDM3 DSP DIMM with 32 Channels"

PID: PVDM3-32          , VID: V01 , SN: FOCXXXXXXXXXXX

NAME: "PVDM3 DSP DIMM with 64 Channels on Slot 0 SubSlot 4", DESCR: "PVDM3 DSP DIMM with 64 Channels"

PID: PVDM3-64          , VID: V01 , SN: FOCXXXXXXXXXXX

But I can only configure transcode profile with a maximum of 2 sessions.

Conference and MTP profile configurations fail because there is not enough DSP resources.

Is the DSP resource allocation failure the reason for this?

What could be a solutions for this problem.

Thanks in advance...

Everyone's tags (7)

DSP Allocation Issues


maybe you can take a look at this post and use the 'test voice driver' command.




DSP Allocation Issues


Can you have a look at BUG ID CSCsx67255

CSCsx67255 Bug Details
ISDN Call Failure w/ cause 47 after DSP Allocation Failure on Channel 
Symptoms: An outgoing call from an IP phone to PSTN through ISDN PRI fails on a
channel due to a DSP allocation failure (not enough DSPs to support the call).
Subsequent calls through that same channel continue to fail with "resource
unavailable" cause value equal to 47 even after DSP resources have been made
available to handle the call.

Conditions: The symptom occurs on a router running Cisco IOS Release 12.4(15)T8
or higher. The call must first fail with a legitimate DSP allocation error. Any
call made through the same channel as the failed call will also fail.

DSP allocation failures on gateway can be checked through the use of the exec
command show voice dsp group all. The last line of the show
command output includes a counter for "DSP resource allocation failure".

This issue can be seen also in some cases upon bootup. When a gateway is
reloaded, system resources will come up with slightly different timing. If, for
example, a PRI interface comes up before the DSP resources have fully
initialized, there may be a similar failure.


1. Reload the router to clear the channel. If a reload cannot be done, busy out
the channel with the failed calls using the isdn busy
b_channel command under the serial interface.

2. If this issue is due to oversubscription of the DSP resources, change the
configuration to meet the DSP resources available on the gateway. Further
information can be found with the CCO "DSP Calculator" at

3. If the issue is related to timing issues upon reload, shutdown the
voice-port in question before reloading the gateway. When the gateway comes
back up, take the voice-port out of shutdown.



Regards, Alex. Please rate useful posts.
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