I am configuring elysia_cron on a Rackspace Managed Cloud Server. We have a loadbalancer in front of two webservers. Am I supposed to use all three (3) IP addresses (Load Balancer, Web01, Web02) in the "Allowed Hosts" field? or just use the IP address of the Load Balancer?
I think you'll find you only need to allow your web nodes, not the balancer.
You may also want to read up on how Elysia handles cron access; allowed hosts is intended to avoid external cron calling. Is this something you are want to exclude? If you really need to secure your servers, Elysia also allows you to set a cron_key to restrict access.
However, it sounds like you're just looking for a recommended default setting.
Edit: On Deer Hunter's suggestion, I could elaborate that the standard configuration is for a cron job, running on the machine on which Drupal is installed, to 'hit' Drupal cron by issuing a get request for cron.php. Thus on an HA deployment, this request originates from a web node. Unless you foresee needing cron to be triggered across the public internet, you only need your web nodes white-listed. HTH.