We have a tedious issue, when performing an EC2 scan's, the appliance identifies the hosts but once the scan completes is says "no hosts alive" and from 54 host's scanned 18 have "no host alive" connection. The ports and security allow communication to Qualys and there are no issues with this side as the Qualys console can connect to the appliance in AWS and the IP.
However, the instances are showing in running “STATE”, when checked in "AWS", connection SSH is OK But it should be scanned by Qualys devices and error message’s am getting is that “host not alive” as it is being blocked from getting a response from the device. It starts to ping and then it should send/sends out a brief UDP and TCP common port mini check and if no further response is received, its marked as down.
This is affecting number of instances in our environment's, am running out of idea's what could be causing this issue across few environments and scanners working fine. I have logged a case But nothing concrete yet from qualys. The host which are STOPPED, those wont be scanned which am aware of But other's are causing major issues, which are in running state.