Teams Direct Routing - inbound drop after 15 seconds

62129738 2 Reputation points

I have an education Tenant with Direct Routing enabled. Connecting to two different SBC, in two different networks.

When a user is logged on with a Polycom phone and receives a call - the call is answered and drops in 15 seconds - without any audio. All other devices work.

In Teams Reports the call - however with SipFinal Code 410, subcode: 531004, code phrase:'IceConnectivityChecksFailed'

Testing done to date:

Same phone on different tenant is fine - rules out phone?
Same Tenant different SBC- rules out SBC? - the second sbc we use is used by multiple clients without issue.

When comparing phone logs for working tenant and failing - the only major item i notice is almost NO candidates being offered by MS when audio does not work.

Any ideas


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  1. Sharon Zhao-MSFT 25,066 Reputation points Microsoft Vendor


    Does this issue persist all the time? Or what changes do before happened?

    Do all callings with the first SBC have the same issue?

    Above all, verify the connection between first SBC and direct routing.

    • To validate the pairing using outgoing SIP options, use the SBC management interface and confirm that the SBC receives 200 OK responses to its outgoing OPTIONS messages.
    • To validate the pairing using incoming SIP options, use the SBC management interface and see that the SBC sends a reply to the OPTIONS messages coming in from Direct Routing and that the response code it sends is 200 OK.

    If the result is failure, please inspect the configuration of the first SBC.

    Meanwhile, you could check the health dashboard for Direct Routing in Microsoft Teams admin center > Voice: Direct Routing. Then, analyzing the information by this article.

    Besides, check UDP 3478-3481 ports and TCP 443 port are open in firewall.

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  2. 62129738 2 Reputation points


    Solution has been found after months of backwards and forwards with Microsoft Support on various levels.

    It appears there are certain forests for Office 365 which DO NOT contain Media Relays or something else related... One such forest is emea-ed4-a4

    To find this you can run the following

    Get-csonlineuser | ft -property ServiceInstance