Double tone Cisco IP phone.

[silvakizir]

Hi to everyone.
I have a CUCM connected via SIP to a CUBE and a SIP Trunk from the CUBE to the ITSP.
I have 2 Cisco IP phones with expansion modules and when they make a call to outside every time they hear a tone they hear a second immediate tone. In conclusion they hear double tones.The specific phones have 2 lines, first line is personal in each "101" and "102" and second line is a shared one which is the central line let's say "100". I put the shared line "100" to a spare ip phone with no other lines and the result was the same double tones. The calls are all successful no matter the double tones.
In addition this happens only to these 2 phones as other phones work properly. Unfortunately I did not find anything on the net.
Any help is appreciated.

[Chris Deren]

Are you referring to "secondary dial tone"? If, so that is typically desired to mimic traditional digital/analog lines, and normally the secondary dial tone defined as "provide outside dial tone" on patterns is enabled to provide the secondary dial tone after pressing the off-net access code, i.e. 9. So user goes off-hook hears dial tone, dials off-net access code and hears secondary dial tone.  Many times the secondary dial tone is heard after more than one digit which implies misonconfiguration of the system where other patterns create overlaps with patterns starting with the off-net access code.

[silvakizir]

No dear Chris Deren,

I am not referring to the secondary dial tone. In every single tone I hear a second immediate tone like this -> beeb-beeb...4 secs silence...beeb-beeb..4 secs silence..beeb-beeb...

Other phone when calling outside I have -> beeb...4 secs silence...beeb...4 secs silence...beeb

Thank you.

[Chris Deren]

Sounds like the phone is configured with another country's network locale as you are referring to ringback cadence which varies between regions/countries.  Review the phone/common device config assigned to the device to ensure it matches desired network/user locale.

[silvakizir]

The CUCM was previously configured to connect to a pri line through H323 Gateway and everything worked fine. This problem occurred when we made the CUCM connect to the CUBEs via SIP and the CUBEs via SIP Trunk to the ITSP.

Nothing has been changed to the phones or the line "100". It must be something with the line "100" and not the devices as when I tried the line to another blank device I had the same exact problem when calling to external numbers.

Thank you.

[silvakizir]

I found the answer with the help of Cisco employee.

It was a bug and we need to put the below command in outgoing to the ITSP dial peers of both the CUBES.

Router(config-dial-peer)# voice-class sip block 180 sdp absent
For SIP-SIP call legs, on the outbound call-leg, applied the command to block 180 (without SDP) messages.

But disabling this could cause blocking all the 180 messages without SDP from the UAS (ITSP). Since there is double ringback heard from the ITSP side it should not cause any issue in my scenario.