Why am I getting a error creating my security group when it only has one rule?

Question

I'm creating a AWS security group with one rule, yet I'm getting an error The maximum number of rules per security group has been reached. I literally just have one rule, so this error seems ridiculous.

Answer 1

I found the issue, I was using a prefix list with a maximum entries higher than our "Inbound or outbound rules per security group" quota.

If you have one rule referencing a prefix list with X max entries, then it counts as X rules. This leads to silly situations like a single rule with a prefix list with a single IP counting as hundreds of rules because you set the max entry setting in the prefix list.

https://docs.aws.amazon.com/vpc/latest/userguide/managed-prefix-lists.html