Ucm6204 no Audio at all


I cannot make this UCM6204 to work. I can register phones local and remote and hear ringing on both sides, but no audio. No audio between extension(local), no audio inbound or outbound DID. I have been through all the NAT possible combinations, NAT on/off on trunk, phone, SIP and so on. I did capture and the SIP headers are appropriate and gets 200OK with all calls but no audio. Even calls to inbound DID gets 200 OK but no audio.
Please help.
UCM6204 V1.7A
Part Number
Version Information


first you need to update the UCM firmware,
then you have to make sure you have audio between two-way and regular local extensions, then you can worry about the rest.
Not having local audio is already a big problem. Remove nat on local extensions on UCM


firmware is updated to latest version. Boot
No change, still no audio.


I didn’t write you “update the fw and you fixed”, I wrote you that you need to update the firmware, but you need to fix the local audio problem first, which is a very serious thing,
If you have problems you should open a ticket or contact a professional in your area.


look at pbx settings, sip settings, nat and fill out the fields and add your local lan at the bottom of the page.


Can you confirm the handset is plugged into the handset socket at the back of the phone and not headset.


among the various hypotheses there is also the advice given by @Telecomsolutions , try to call 2 phones and answer on both hands-free, so you see immediately if audio is correctly and bidirectional.


Thanks for the comments everyone. I opened a ticket with support. I will update once I get an answer.