I have two CUCM server in a cluster ( 1 Publisher & I subscriber) . I defined one call manager group called "CMG_Prtoduction" and have added subscriber as first CM and Publisher as second CM. I have created a device pool called "DP_Production". DP_Production is set to use CUCM Group CMG_Production. All our phones are set to use device pool "DP_Production". All phones are obtaining IP automatically from DHCP. DHCP option 150 is set Publisher first choice & Subscriber second choice which I believe is used for phone configuration file.
I took subscriber of the network and found 60% phones (1700) failed over and registered with publisher but about 1500 phones couldn't register at all and were displaying "Registering" message on the phone. Please help on " How to troubleshoot / rectify this type of issue"
Action Taken - I have checked the access-list / connectivity issue and all looks in order. I defined a new vlan and dhcp scope. I setup a test phone in new vlan. I set dhcp option 150 as Publisher only. I created a Call Manager group CMG_Test and only added Publisher in the list. CMG_Test "Auto-registration Cisco Unified Communications Manager Group" setting is not checked. I created a device pool called DP_Test. DP_Test is set to use CMG_Test. Test phone doesn't register at all and continues to show "Registering message" but as soon as I add subscriber to CMG_test test phone registers with subscriber.