AWS VPC Design issue - CIDR conflicts
I am planning to create subnets on this newly created VPC. At the moment, I have created four subnets on three AZs and fourth one kept as spare.
I would then break each of the four subnets and create subnets inside those for public and private purpose. To give an example:
10.0.0.0/18 — AZ A
10.0.0.0/19 — Private
10.0.32.0/19
10.0.32.0/20 — Public
10.0.48.0/20
10.0.48.0/21 — Protected
10.0.56.0/21 — Spare
This will be repeated for all other ones. The complete picture will look like
10.0.0.0/16:
10.0.0.0/18 — AZ A
10.0.0.0/19 — Private
10.0.32.0/19
10.0.32.0/20 — Public
10.0.48.0/20
10.0.48.0/21 — Protected
10.0.56.0/21 — Spare
10.0.64.0/18 — AZ B
10.0.64.0/19 — Private
10.0.96.0/19
10.0.96.0/20 — Public
10.0.112.0/20
10.0.112.0/21 — Protected
10.0.120.0/21 — Spare
10.0.128.0/18 — AZ C
10.0.128.0/19 — Private
10.0.160.0/19
10.0.160.0/20 — Public
10.0.176.0/20
10.0.176.0/21 — Protected
10.0.184.0/21 — Spare
10.0.192.0/18 — Spare
I have followed this link Practical VPC Design for the above plan.
However, I have getting error as CIDR conflicts. I was wondering whether you can help.
I am guessing that you have created 4 of these: 10.0.0.0/18 and by doing so you have "spent" all of the resources.
You would need to create subnets as follows:
AZ A
10.0.0.0/19 (8192) - Private
10.0.32.0/20 (4096) - Public
10.0.48.0/21 (2048) - Protected
10.0.56.0/21 (2048) - Spare
Total: 16384
AZ B
10.0.64.0/19 (8192) - Private
10.0.96.0/20 (4096) - Public
10.0.112.0/21 (2048) - Protected
10.0.120.0/21 (2048) - Spare
Total: 16384
AZ C
10.0.128.0/19 (8192) - Private
10.0.160.0/20 (4096) - Public
10.0.176.0/21 (2048) - Protected
10.0.184.0/21 (2048) - Spare
Total: 16384
AZ D
10.0.192.0/18 (if you want to divide this one, you will need to delete this subnet and create smaller chunks.
Total: 16384
===================================
Grand total: 65536