1

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?

1
  • /28 is 16 addresses. 0-15, 16-31, etc. (0 and 15 -- all-zeros and all-ones addresses -- are reserved for network and broadcast)
    – Ricky
    Jan 8, 2021 at 2:20

1 Answer 1

4

Isn't it's range 10.0.15.15 to 10.0.15.30 which is within the VPC?

Yes, but it's not a valid /28.

10.0.15.0/28 or 10.0.15.16/28 are valid ranges.

4
  • 2
    For more details on CIDR subnetting, check out this primer over at Server Fault: serverfault.com/questions/12854/cidr-for-dummies
    – RobinG
    Jan 7, 2021 at 19:06
  • Why isn't it a valid /28 and why should it be a multiple of 16 ? Jan 7, 2021 at 19:08
  • 1
    A /28 subnet requires the lowest four bits - the host bits - to be all zero.
    – Zac67
    Jan 7, 2021 at 19:16
  • 1
    @AkramElectroTech, if you read and understand this two-part answer, you will see where you have gone wrong.
    – Ron Maupin
    Jan 7, 2021 at 21:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.