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Community Member

Unexpected Calls from Cisco

Hi all,

We have several customers who work off a 121 NAT configuration who are receiving missed calls from Cisco. This appears to be coming through as a telephone call and happening quite sporadically.

Any suggestions other than blocking source from the router? It is quite difficult to pin point an address as only Cisco is shown.

Thanks in advance


VIP Super Bronze

This is a result of external

This is a result of external sources trying to exploit possible PTSN trunks in users environments, it's being seen by a lot of people that have video or telephone systems that are accessible on the public internet.  You can read a bit more about it in this discussion: sourceh323idcisco-incomingcalls.  Only thing that can be done is if you're using a call control server such as VCS you can create a call policy to block the call attempts (there is one I created in the linked discussion), or if the system is stand alone as it appears you're is, block all incoming IPs traffic to the codec except those you trust to allow in.  You could get the IP by going through the codec's call history, however that won't help as the source IP changes constantly.

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