Private IP Address Ranges
IP addresses used for provisioning the phones must be allowed in RFC 1918 (10.0.0.8 /16, 172.16.0.0 /12, 192.168.0.0 /16). If the IP address that is used for provisioning phone is other than the ones allowed in RFC 1918, the phone provisioning fails. To avoid such phone provisioning issues, you must enter the IP addresses in the Private IP Ranges page. You can add individual IP address (host address) in the x.x.x.x format or an IP address range (subnet) in the x.x.x.x /n format.
Cisco Partners can add IP addresses during the initial site deployment on the Private IP Ranges page. Post site deployment, both Cisco Partners and Customer Administrators can add private IP addresses, under Manage Sites > Settings > Private IP Ranges.