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Dialing Zoomcrc from a Cloud Registered WebEx Room Kit



We're having a problem calling into Zoom meetings from cloud registered endpoints. We are not having the problem with on-prem registered end points.


Call Flows

Cloud registered end point -> HybridCalling-ExpE --> HybridCalling-ExpC -> CUCM -> MRA-ExpC -> MRA-ExpE -> internet

On-prem registered end point -> CUCM -> MRA-ExpC -> MRA-ExpE -> internet


-As you can see from the call flow examples above the cloud based end points use two additional Expressways.

-When I dial the zoomcrc address from the on-prem registered endpoint I get prompted for the meeting passcode and am admitted to the meeting

-When I dial the zoomcrc address from the cloud registered endpoint it initially seems to connect but I never get prompted for the meeting passcode and it drops after about 2 minutes.

-I can see the call from the cloud registered endpoint is passing through all the expressways.

-From the Zoom meeting I can call the Cloud Registered units SIP address and it connects to the meeting. This connection from Zoom to the Cloud Registered Room System stays in the cloud and does not pass through our environment. Outbound calls from the Cloud Registered Room Kit to Zoom pass through our environment because we're using Hybrid Calling for our cloud registered endpoints.


Versions: CUCM: System version:

Expressways: X12.5.2


If anyone has seen this before or has any thoughts on what the issue may be I'd appreciate the feedback.


Thank you,











If you locate an answer to this, I am interested. We are encountering the exact same issue.


We are having this exact issue. Did you ever find a solution to this?

For us it ended up being certain ports on the firewall were being restricted. Odd that it worked on-prem calling traversing the same firewall, but used a different set of ports with Hybrid Calling and Cloud Registration.


Ended up requiring a combo troubleshooting session between Zoom Engineer, TAC Engineer and Internal Firewall Team. Once we got everyone on the call, we could see the call signaling traversing correctly but media was not. Advice from Zoom Engineer pointed us to the following knowledgebase:


After ensuring all ports were allowed to the Expressways, situation resolved.