In the first instance, upgrade. There is a major security problem with 2.1.x release. Get 2.2.x onto your system asap.

What are your NAS (cisco controllers) timeouts? Is this box a pure proxy or does it do authentication too? Have you enabled ciscos status-check system so it knows the RADIUS server isn't dead but just hasn't had a remote response yet?

Around 67% of eduroam sites in the UK use freeradius

alan