Cisco SX20 with ISDN Link : Receving calls from an unknown/strange numbers

[jcatimpo14]

Dear Readers and Guru's,

We are using a Cisco SX20 with ISDN Link due to some our regional offices still using ISDN connection, anyways, this is working fine. The only problem I am experiencing is the fact there are a lot of unknown established calls, examples below ;

1003, 3500, 100, 7070, 1003 and etc..

the format of the incoming call will start with an unknown number and followed by our SIP number ; 1003@***.**.*.***:5060

I want to permanently block this unknown callers as this is so annoying during our Video Conferencing meeting it keeps on ringing on the screen..

I was told that it has something to do with the network/firewall settings but honestly i don't know where to start.

i had attached a screenshot of the unknown numbers we are receiving.

TIA guys.

[Leo Laohoo]

Duplicate post. 

Go here:  https://supportforums.cisco.com/discussion/12217626/cisco-sx20-receiving-incoming-calls-unknown-sources

[Devasayee Gopalan]

Hi,

In codec , can you try the following config. change and check if the unknown calls are stopped ?

system configuration -> SIP -> ListenPort -> Off

Thanks,

Deva G