#subnetting
CIDR maths for real networks, including the five addresses AWS reserves in every subnet and what that does to the sizing arithmetic you were taught.
2 articles tagged #subnetting, newest first.
100.64.0.0/10 in AWS: Using CGNAT Space to Fix EKS IP Exhaustion
When an EKS cluster runs out of pod IPs and the VPC has no RFC 1918 space left, a 100.64.0.0/10 secondary CIDR is the fix. Why AWS allows it, and what breaks.
Why AWS Reserves 5 IP Addresses in Every Subnet (and What Each One Does)
AWS takes five addresses out of every VPC subnet: network, router, DNS resolver, one in reserve, and broadcast. What each is for, and how it changes sizing.