No ringback on caller side when calling any DID

[CarlosPrex]

Customer has a R5.2 centralized
On a local site, has a 8500 server with DS1 Trunks, Medpro/Clan. Phones are analog/digital/ip phones.

Customer is having issues when external callers dial through the local DS1 lines and no ringback is heard ONLY ON CALLER SIDE, so caller thinks the call is not being connected and hangs up before the call is answered (the call rings properly on the phones, no matter if it´s analog/digital/ip).

I created a VDN with a DID and the vector pointed to hear ringback during 999 seconds.
When the VDN is dialed from outside ( DID through DS1 Trunks), no ringback is heard on the caller side, but I can see the trace indicating the call is ringing on the vector.
When someone calls the VDN from any extension, the ringback is heard as it should.

Any suggestions?

Thanks in advance.

 

[dialtonebone]

Did the list trace show anything? Did you verify the RTP paths in the list trace are allowed by the network?

 

[phoneguy55]

CM5.2 is very old and there were a bunch of service packs. I would start by making sure firmware is the latest for CM and TN cards. Make sure the ds1's are running clean. No CM alarms.