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CareyKnightonFitt-3540 asked ·

Teams Direct Routing - inbound drop after 15 seconds

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 Answer

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SharonZhao-MSFT answered ·


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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Thanks for the response..

I am pretty confident the SBC's are configured fine.. The only reason I added the client to the second sbc was to rule out the clients on premises firewall causing the issue.

The azure based sbc has all the required firewall ports open and its only the polycom phone that is having the issue - all other calls are fine.

Compared results from get-csonlinepstngateway from a working tenant and the non working tenant and all identical.

The Azure SBC is connected to the working tenant and the non working tenant. in the same way.


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I have rechecked the firewall and all source ports are allowed in destination ports of sbc/
I have added 443 tcp and 3478-3481 udp.. on the sbc - however not sure if those are required? - as incoming destination.


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It recommends you contact Polycom engineer to check if there is any error in Polycom Phone.

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Do you have any update now?

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No update yet - call is being logged with polycom.
Microsoft support are saying its cause polycom is not teams certified.

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SharonZhao-MSFT avatar image SharonZhao-MSFT CareyKnightonFitt-7946 ·

This article lists IP Phones certified for Microsoft Teams. Polycom isn't included in it.
It recommends you use other certified IP phones now. Meanwhile, Microsoft is announcing the availability of new IP phone hardware that will be certified for Microsoft Teams.
Your time, understanding and cooperation will be highly appreciated.

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