Most calls with Teams Direct Routing become one way audio

New Contributor

Have set up Direct Routing with an Audiocodes SBC and am testing features with my account in Teams only mode.


I can make and receive calls just fine but it seems on most calls after about a minute or so the audio becomes one way - initially the call would just drop and I saw in the syslog the AC was showing an rtp broken connection error so I set broken connection mode to ignore but now the audio just becomes one way where I can hear the remote person but they can't hear me. Audiocodes syslog isn't helping much and just shows an rtp broken connection error.


Anyone else see this or have any ideas? I would suspect it's the firewall except for the fact that in some of my testing the calls are fine and don't become one way.

9 Replies

Hi @jguel, where is your SBC deployed? Is it nat'ted? In case there is NAT used: did you configure NAT rules on the SBC, too?

There is a good blog post regarding SBC Teams Direct Routing and NAT here:

It is NAT'd and I do have NAT rules set up. I don't think that's the problem because as I said the audio is two way in the beginning of the call and only becomes one way after a minute or two. Plus it's not every call but it is most calls.

I am having this issue with Audiocodes SBC but its after 15 min.  Wondering if you were able to find a fix? @jguel 



Determined it was a firewall issue - the firewall engineers could not figure out why it was happening but it was definitely firewall. Why it was so intermittent for us though I don't know. Way I figured that out was convinced the network guys to instead of NAT'ing the IP and Interface that was connecting to Office 365 was to not NAT it and assign the public IP directly to that interface and put it on the outside so it bypasses the firewall completely. Once this was done everything worked. Since that fixed the issue I convinced them to just leave it like that as the SBC has it's own ways of mitigating unauthorized access attempts.


We were using fortigate firewalls if that helps. If you are having this issue and you are using a NAT try what I did and see if it fixes the problem.

15 minutes sounds like session timer or srtp re-keying related, to me. Do you use a secured connection with Sip TLS and SRTP?
You might want to check the IP Profiles and the Media Security settings for the trunks on the SBC.




I am facing the same problem, after 15 minutes. One-way audio occurs.
The connection path is
IP phone --- PBX --- audiocodec SBC --- firewall --- Internet --- MS team client

Anybody can resolve it?

had this very issues years ago with Firewalls. I had to get Juniper to write a patch. The issue is the firewall see the voice packets as a DDoS attack and terminates the session, It happened every-time at the 15minute mark. Check the DDoS setup on the firewall and make sure it knows the ports being used for voice services.

@Leigh Andrews was this for all calls? We are having an issue where incoming calls drop all audio at the 15 minute mark, can be replicated every time when executing this call scenario. 


Traffic is going through a Fortinet firewall.