Xcellence IT on "[Plugin: W3 Total Cache] 403 errors when using CDN"

I am using MaxCDN and recently got a 403 errors when any resource is requested from the CDN. If resource is requested directly then it is served correctly but not from CDN.

MaxCDN support asked me to whitelist few IP addresses. Can you please advise how can I whitelist those IP addresses?

http://wordpress.org/plugins/w3-total-cache/