Atlantis ILIO Center can monitor the health and availability of ILIO Session- and Replication hosts. If necessary ILIO Center sends alerts via SMTP (aka Mail) or via a SNMP trap (push). However, if the ILIO Center experiences an unexpected shutdown or network connectivity is lost, a SNMP trap is never sent (or in case of lost of network connectivity: the monitoring system does not receive the trap).
Additional monitoring can be done via ping or by monitoring the state of the VM. However, verifying the availability of a machine via ping could result in false-positives and not each monitoring system can monitor the state of a VM, therefore you might want to monitor via SNMP polling (pull).
A vanilla installation of Atlantis ILIO (Center) does not have an SNMP agent installed, therefore I wrote a script that can push the agent and/or update the configuration. You can find the download at the bottom of this article.