How many phones and directory numbers can be configured on Cisco Unified Communications Manager Express by default?
Yes, by default, no ephones or directory numbers can register. Before doing anything else, the following configuration is required:
This allow up to 4 phones to register / be configured and 8 directory numbers.
If you don't do this, the router will not allow ephones or ephone-dns to be created. Here is an example of what would happen:
ephone tag 1 exceeds max-ephones 0
dn 1 exceeds max-dn 0
The maximum number of ephones and ephone-dns that can be configured is platform dependent. Here is an example of my router that can support 30 phones with up to 150 ephone-dns:
Maximum phones to support
Maximum directory numbers supported
Cisco have a great document showing you how many ephones/dns are supported on specific platforms. Have a look here
As an example, using CME version 4.3:
The 2801 supports 25 phones and 120 ephone-dns
The 2811 supports 35 phones and 144 ephone-dns
The 2821 supports 50 phones and 192 ephone-dns
The 3845 supports 250 phones and 720 ephone-dns
(There are others, please refer to the link above for a full list)
Cisco also recommend that you only enable the number of ephones and ephone-dns for the number you require, not the maximum the platform can support. The reason is that when a ephone / ephone-dn is created, it uses up memory on the router. Don't just create them because you can! Create only what is required.
To your success!