Cisco Compatible Extensions (CCX) is a Cisco specification for IEEE 802.11 Wireless LAN based client devices. There are currently four versions of the Cisco Compatible specification: Version 1 (V1), Version 2 (V2), Version 3 (V3), and Version 4 (V4). The details of the CCX specification can be found at the Cisco web pages:
Most of the Nokia Eseries devices and also some other Nokia devices (e.g. N79, N85, Nokia 5800 XpressMusic) have been officially verified to conform with Cisco CCX specification (usually either CCXv3 or CCXv4 compatible). The latest status for the Nokia devices can be viewed at the Cisco Compatible Extensions Client Devices web page:
Please, note that the above list contains only the devices which have been specifically tested and verified. The corresponding WLAN functionality is available also in other Nokia devices but these devices haven't gone through the official testing process.