Why does this give me an error "must be valid ipv4 cidr"?

Question

If I set up an AWS VPC with CIDR of 10.0.0.0/20 then the range is 10.0.0.0 to 10.0.15.255
I make a subnet now. Why does 10.0.15.15/28 give an error. Isn't it's range 10.0.15.15 to 10.0.15.30 which is within the VPC?

Answer 1

See this site for some help. 10.0.15.15/28 is 10.0.15.0 to 10.0.15.15. Perhaps you wanted 10.0.15.15/27 which goes to 10.0.15.31.