Alibaba Cloud Elastic Compute Service (ECS) instances in different Security Groups will definitely have no...

Alibaba Cloud Elastic Compute Service (ECS) instances in different security groups are isolated from each other by default, but they can communicate with each other if the security group rules allow it. A security group is a virtual firewall that controls the inbound and outbound traffic of ECS instances. You can configure security group rules to specify which IP addresses, protocols, and ports can access the ECS instances in a security group. You can also authorize other security groups to access the ECS instances in a security group, which enables cross-security group communication. References: Manage ECS instances in security groups, Security FAQ, ECS Security Groups - Alibaba Fundamentals