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Unknow number calls and fax tone


We are seeing a very peculiar problem. One of the IP Phone (7970) is receiving calls from an unknown number. On answering, a fax tone is heard on the other end. We ran a filtered CDR search by extension and found "null" in the Calling No column. I believe that the ANI information is blocked at the telco if the privacy bit is set to ON but needed some suggestions on making sure that the call is not internal.


Re: Unknow number calls and fax tone

Hello Nelson,

Have you tried to check the CCM traces? After the user reports the problem, get the traces for the exact time when the call was received and look for dd=; this will give you the TCP Handle to trace the call. If it comes from a GW, it will show you the name of the endpoint/GW where the call came from.

Hope this helps!

Community Member

Re: Unknow number calls and fax tone

Hi Esteban,

Thank you for the response. Since this is the first time I will be setting up the traces, can you please guide me in the right direction as to which specific service I should be looking at. The relevant services I can see are the Call Manager, CDR Agent and CDR Repository Manager.

Also, can you provide a step by step of whats to be done in the RTMT tool. Appreciate your help.

Hall of Fame Super Red

Re: Unknow number calls and fax tone

Hi Nelson,

Just to add a note to the great tips from my friend Esteban, if you want a really quick way to check this out instruct to user who is getting these calls to Transfer the next one to your Fax number. You can print the Fax and look at the Header info as well the content to determine where these are coming from.

Hope this helps!


Community Member

Re: Unknow number calls and fax tone

Hi Rob,

Thanks for your response. We are not sure if these are fax calls. The only reason I called them that is because of the tone that is heard from the other end. Therefore we are trying to identify the source caller and then find out what it really is.


Nelson S

Community Member

Re: Unknow number calls and fax tone,M1


I have linked a book that should be able to answer a lot of your questions about how to trouble shoot this problem and procedures. If you search for TCP handle or CCM trace or RTMT you should be able to find what you need.

(This is a Google book so some of the pages a omitted but it should give you what you need)

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