Hi,
Your Phone tries to net-load its configuration from you
Cisco Unified Communication Aplliance.
The CP-52X Phones are for the Cisco Unified Communication System,
not for SIP (and asterisk) . Yes, the look very much the SPA- Version.
For SIP, use the (formerly Linksys) Small Business Phones
SPA-9XY .
With SPA 922, 942, 962 you will get backlight display and more cpu in the phone
so they may built SSL/TLS Connection to their Centrex.
(and they will be PoE, so you may need to order the external powersupply).
With SPA 921, 941, you will get NO Backlight and NO non-english Menues.
I personally recommend the SPA525G which has color-display,
5 lines, works with SIP or with Cisco Unified Communication
or with the SPA9000 IP-PhoneSystem
(it's POE, order an external powersuply).
Missing is just a li-ion accu pack since the phone can work over WLAN.
It may also user your ldap/active directroy for retrieving phone numbers.
(AFAIK also on the SPA-9x2 phones possible).
Jürgen.