Details
Critical Description
When configuring basic networking, by default the network is created with the "DefaultSharedNetworkOffering". This offering does not have a security group. No inbound traffic is allowed to the created VMs. Reading the AdminGuide documentation:
"Each CloudStack account comes with a default security group that denies all inbound traffic and allows all outbound traffic. The default security group can be modified so that all new VMs inherit some other desired set of rules."
If a network is created without a security group, it shouldn't have a security group and all inbound/outbound traffic should be allowed - or at the very least the default security group should be able to be configured.