Cisco Support Community
Community Member

Cisco IP Telephones appear to call themselves

Hi All

I've learnt a hell of a lot from this community and so in the interests of sharing and giving something back, the following may save you some time and head scratching. On the flip side, there is also the risk of telling you something that you already know:-

Our setup in CUCM 7.1.3 and predominantly 7941's and 61's. I’ve just had to deal with a couple of support desk calls where the clients reported that they had several missed calls shown as from their own phone. In both cases the missed calls originated from the full DDI of the telephone extension. For example if it were my phone, the call records will have shown that 01752 588714 called 88714.

The Call Detail Records in Call Manager confirmed that these extensions did appear to receive calls from themselves at the times reported. However, I doubted that this was the case because we withhold our Caller Line Identity (CLI) on outbound calls. If the call had originated from within the University, we should not have seen the CLI. Having trawled through the Call Detail Records (CDRs) for each of the five gateways that could have placed the call to the PSTN, it became clear that the calls did not originate from within the University.

It turns out that if you send an SMS text to a land line, British Telecoms’s  “SMS Text Delivery System”  displays the CLI of the calling party as that of the called party. – i.e. the phone appears to be calling itself. I’ve sent my own desk phone a series of SMS text messages and can confirm the same. Both phones showed several missed calls as this happened out of hours and the SMS Text delivery service continually re-tries to deliver the text message. 

It certainly had me foxed for a bit.


Network  Operations and Telephony Team

Information and Communications Systems

Information and Learning Services

Plymouth University

CreatePlease to create content