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Question regarding CUCM group and phone registration

We have CUCM 7 and a cluster of three Call Manager servers




My understanding is that

When a Cisco phone boots, it gets an IP Address via DHCP and is told which server to register to, once it gets a configuration file.

According to the group shown above, the phone will regsiter to Sub and if it is unavalable or lost, will try SubDR next, then Pub.

What happens if you have a non cisco phone that is configured in call manager to use the above CUCM group,  Sub is up and has phones registed to it, but within the config of the non cisco phone, it is forced to Pub (Pub is up) for it's call manager setting?

The phone is pointing to Pub and tries to go there, but call manager says it should be using Sub first.

Should the call be processed because Pub is in the cluster and working, or not processed because the cluster thinks it should be going to Sub first?

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Re: Question regarding CUCM group and phone registration

In this example the call will be processed. The decision on which node to register to is up to the end point. With Cisco phones, UCM provides the order that the end point should follow through the TFTP config file. The UCM nodes do not enforce this order because there is no way to be sure that, from the perspective of the phone, one of the more preferred nodes is not unreachable. Since third-party end points do not use that process and you specify the server address(es) directly on the device, it will start with whatever you assign.

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