I'm sorry if this is a noobish question. If you have some cisco switch connected to d-link wireless access points, which acts as the Radius client?
Whichever is acting as the "Authenticator" (https://en.wikipedia.org/wiki/IEEE_802.1X#Overview).
The main parts of 802.1x Authentication are:
- A supplicant, a client end user, which wants to be authenticated.
- An authenticator (an access point or a switch), which is a "go between", acting as proxy for the end user, and restricting the end user's communication with the authentication server.
- An authentication server (usually a RADIUS server), which decides whether to accept the end user's request for full network access.
From this it looks like you can have the switch authenticate the access point (to prevent someone plugging in a different access point) but that the access point itself could be authenticating the clients too.
The switch would likely only authenticate what is plugged into it and I doubt would be wireless client aware.