BSNL FTTH VoIP One-Way Audio Issue

  • Thread starter Thread starter shreeshagh
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Hello Everyone, hope you all are doing well.
Recently, I got a new BSNL FTTH installed at my office. It's working fine compared to my earlier ISP.

I found out that there was an option to configure my modem ( Syrotech SY-GPON-1110-WDONT ) as a SIP Trunk that's used to make VoIP calls. Found few resources to configure it and I'm able to connect to the Trunk with my SIP Client. I'm also able to make or receive calls.

The problem is that my voice is inaudible to the person I call (complete silence). So, I thought it might be issue with BSNL and connected an analog phone directly to my modem and it's working fine. I contacted BSNL and they are totally unaware about how VoIP works. I suspect it has something to do with the codecs or something advanced. Please help me out. I've attached the screenshots of my configuration.




Try changing the VLAN Id for Voice_Internet profile to 1830.

Most probably, the moment you apply those settings, the default gateway will change too, so you'd have to change it in the static route too.

Also, please post the screenshot of the voice_internet profile page.
Thanks for replying.

As you suggested, I changed my Vlan ID to 1830 and Voice_Internet profile changed its status to "down". The VoIP status was showing "registering" for several minutes until I changed the Vlan ID back to 1831.

Attached the screenshots of the voice_internet profile page.

Which sip client app are you using ?
And which firmware version are you using for ur Ont?
I also faced the same error in zoiper 5 after configuring my cousin's Netlink ont (323 rgw). Then I updated the firmware version of the ont to 1.0.35 and now zoiper is working fine.
I'm tried several SIP clients. First Zoiper (didn't work), MicroSIP (didn't register at all), now trying to use a physical IP Phone that has very complicated configuration. Everyday I spend hours figuring out how to configure.

Where did you get the firmware image ?
I got the firmware image from Netlink's official site(Netlink firmware). This firmware might work for you too because companies like Netlink, Syrotech, DBC, Digisol imports their ONTs from Chinese Manufacturer/Company V-SOL and later rebrands and distributes them in India. All these ONTs have the same hardware and same firmware/Web interface.


You can contact Syrotech and ask them to email you the latest firmware for your ONT.

Can you share the device info page of your ONTs web interface where the hardware and software version is mentioned?
Okay, the hardware version of your ONT is different mine is v1.0. So it is better to contact Syrotech before flashing any random image file.
Pls blackout/block important information like serial no, password, IP address, telephone no before posting images on this forum.

In the meantime, you can follow these for configuring your device


you can also take help from @sloj and his thread- FTTH VOIP SIP Softphone configuration with ONT/ONU. (Now works on some more apps) | BSNL Bharat Fiber Broadband

And last, here is my thread - Configuration for VOIP/SIP calls( using Zoiper/GS Wave) on Huawei ONT and TP Link Router. | BSNL Bharat Fiber Broadband