All,

We are migrating from CUCM 8.5 --> 10.5. As we have a mixture of phones on both systems, we cannot change DHCP option 150 to point to 10.5 without causing outages to the phones that should still be registered on 8.5. Thus, we are using the "Alternate Cisco File Server" on 8.5  that will forward a configuration file request to 10.5, if 10.5 contains a device's configuration file, the phone will register to 10.5. This feature is working just fine with 79XX and 3905 phones, are there any caveats with 88xx phones? We cannot get it to work with those models. I think that I heard that 88XX phones request their config file a different way than older phones, so this might the problem. Any help is greatly appreciated.