Extension to extension voice issues on hosted phones fed off Fortiswitch

[stewarta]

We recently converted to a new cloud hosted phone solution with Sinch in our office and sense doing so I have had reports of intermittent issues with garbled voice on calls between extensions in the office. All our phones are fed PoE individually from the same Fortiswitch 448F. There are no issues at all with incoming or outgoing external calls which I've dealt with relating to SIP ALG on the Fortigates. With this issue the RTP traffic handling the voice doesn't route through the firewall and I'm at a loss as to what could be causing the issue. We resell and support this product with numerous other business customers and I have yet to hear about an issue like this so I was hoping someone might have some suggestions or feedback on this problem.

[Anthony_E]

Hello stewarta,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[Anthony_E]

Hello stewarta,

We are still looking for someone to help you.

We will come back to you ASAP.

Regards,

[samundson]

Thank you! For some reason I had to sign up for the community account again, so my username is slightly different now. Any help on the issue is appreciated.

[Anthony_E]

Hello Stewart,

At least we can recognize your picture :D!

I will find an expert to help you!

Regards,

[Anthony_E]

So here is the answer from the expert:

"Are the VOIP phones connected on the same VLAN?  If routing is involved we need to investigate this from the FortiGate point of view,  It is better to get a TAC case running for this issue: https://support.fortinet.com/welcome/#/".

I hope it will help you.

Regards,

Anthony.

[samundson]

I realized that I hadn't updated this thread with any new information regarding this issue. After a few months of troubleshooting this intermittent issue I think we have things figured out, but getting there was a painful process.

I engaged Fortinet TAC regarding the issue from both the Firewall and Fortiswitch perspective and chased a few false leads that didn't get us anywhere. While troubleshooting with support we did learn some unknown routing information that helped rule out some possible causes of the problem but we still couldn't pinpoint a solid root cause due to how random the issue arose.

I ended up building and entirely new VLAN/subnet on our Fortigate and bypassed our DHCP server and instead used the Fortigate to hand out DHCP, which was all done based on a suggested next step from support. Even after performing all these changes we were still experiencing the problem.

After a while our technicians started troubleshooting by changing some things with the Yealink phones themselves, such as removed the cradle expansion, headset, etc. At this point there were to many things being changed around the same time to know what might have actually fixed the problem but we're pretty confident that there was a firmware/config update for the phones that fixed the problem without us knowing. We also found issues with several old headsets that our new phones weren't playing nice with and it was causing voice delay, but wasn't related to the other problem at all.

I wish I could provide a more specific resolution to this problem, but this was anything but cut and dry.