I have created a four subnet VPC, where two subnets are private and two public. Instances in the private subnet has only private IP's and reach the the internet through an IGW/NAT GW.
I can successfully create an ECS clusters spanning my public subnets, but when I create a cluster in the backend subnets, the cluster instances are unable to register in the cluster.
I suspect network issues, and I am debugging with Flowlogs. In the mean time, I was hoping someone could shed some light over what ports that need to be open, or other configuration involved in ECS cluster management.
Best Answer
I suspect this is port related, as it's fairly standard that things in a cluster need to communicate. The two articles below should answer this question for you. It seems to me the following are probably required
Note that I know little about ECS and have simply done a couple of Google searches and read documentation. ECS is based on Docker so I looked at that. Some experimentation will be required.
Digital Ocean has a good article on Docker Ports.
Then the Amazon documentation mentions some of the same ports.
Note that as per Wikipedia and comments below the ephemeral port range may need to be expanded.