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New Member

External Phone Connectivity for IP Phones

We have had an issue occur where external calls would drop or if picked up, would not return audio. It began sporadically and began to happen within an hour to most all of the IP Phones. I used sniffer to track one call which indicated that the call was going to the gateway but not being returned. After recycling the voice gateway, all external phone calls resumed normally. Any ideas on what caused this issue? And if so, is it the callmanager or the voice gateway with the problem.


New Member

Re: External Phone Connectivity for IP Phones

Scott hi,

We the information you have provided, my guess will be that it is a firewall issue.

Please make sure you have all the VoIP ports open adn you are not using NAT in your LAN.

Can you be more specific as for you network enviorment?

New Member

Re: External Phone Connectivity for IP Phones

Depending on what gateway you are using, the problem sounds like an existing bug in the DSP. The NM-HDV for the 2600/3600 has this problem.

You can look at the DSPs and determine which are having a problem and lock them out, but you have to restart the router to clear the problem.


New Member

Re: External Phone Connectivity for IP Phones

Seems like the DSP error was the issue. We are still monitoring. The router began showing DSP errors as calls were being connected at which time they would drop or go through without audio. Turns out our IOS needed to be upgraded. 12.2(7) or high is said to have the fix. Thanks for all the input.


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