tschuy / cidrblocks

cidrblocks

Generate subnets within Availability Zones from a CIDR.

CLI Usage

Only the --cidr flag is necessary. By default, it splits into four availability zones and outputs a table:

(cidrblocks)(master) → ./cidrblocks --cidr=10.0.0.0/20
VPC Range - 10.0.0.0/20

AZ a (10.0.0.0/22):
	10.0.0.0/23 (Private - 512 addresses)
	10.0.2.0/24 (Public - 256 addresses)
	10.0.3.0/25 (Protected - 128 addresses)
	10.0.3.128/25 (Extra - 128 addresses)

AZ b (10.0.4.0/22):
	10.0.4.0/23 (Private - 512 addresses)
	10.0.6.0/24 (Public - 256 addresses)
	10.0.7.0/25 (Protected - 128 addresses)
	10.0.7.128/25 (Extra - 128 addresses)

AZ c (10.0.8.0/22):
	10.0.8.0/23 (Private - 512 addresses)
	10.0.10.0/24 (Public - 256 addresses)
	10.0.11.0/25 (Protected - 128 addresses)
	10.0.11.128/25 (Extra - 128 addresses)

AZ d (10.0.12.0/22):
	10.0.12.0/23 (Private - 512 addresses)
	10.0.14.0/24 (Public - 256 addresses)
	10.0.15.0/25 (Protected - 128 addresses)
	10.0.15.128/25 (Extra - 128 addresses)

The number of availability zones can be specified:

(cidrblocks)(master) → ./cidrblocks --cidr=10.0.0.0/20 --azs=3
VPC Range - 10.0.0.0/20

AZ a (10.0.0.0/22):
	10.0.0.0/23 (Private - 512 addresses)
	10.0.2.0/24 (Public - 256 addresses)
	10.0.3.0/25 (Protected - 128 addresses)
	10.0.3.128/25 (Extra - 128 addresses)

AZ b (10.0.4.0/22):
	10.0.4.0/23 (Private - 512 addresses)
	10.0.6.0/24 (Public - 256 addresses)
	10.0.7.0/25 (Protected - 128 addresses)
	10.0.7.128/25 (Extra - 128 addresses)

AZ c (10.0.8.0/22):
	10.0.8.0/23 (Private - 512 addresses)
	10.0.10.0/24 (Public - 256 addresses)
	10.0.11.0/25 (Protected - 128 addresses)
	10.0.11.128/25 (Extra - 128 addresses)

Unused blocks:
	10.0.12.0/22

It can also output in four formats:

• table
• cloudformation
• terraform
• cli (AWS cli commands) (coming soon)

(cidrblocks)(master) → ./cidrblocks --cidr=10.0.0.0/20 --format=cloudformation
{
	"AWSTemplateFormatVersion" : "2010-09-09",
	"Resources" : {
...

Web Service

Alternatively, cidrblocks can be run as a web service:

(cidrblocks)(master) → ./cidrblocks serve --port=8087

→ http://localhost:8087/?format=table&cidr=10.0.0.0/8
→ http://localhost:8087/?format=cloudformation&cidr=10.0.0.0/8&azs=2

Library

cidrblocks can also be used as a library within another application with the cidrblocks/subnet subpackage.

cidrblocks's Issues

AWS commands

awscli should be an output option.

lib it out!

Main obstacle here: Most applications making use of this library will want to deal with go objects of some sort at runtime, rather than string literals which need to be unmarshalled, modified and re-marshalled in most use cases.

There are some architectural "additions" I'll venture a recommendations towards:

• An intermediate representation (IR) for a generated network layout that can then render to to any of our various output formats (table, terraform, cloudformation). This IR will be the "stable" interface this package will present to dependent codebases going forward.

Later on, perhaps we can extract the individual output formats into implementations behind a common interface and attempt to provide an abstraction layer for actually constructing these configs across providers. Given that there are a lot of different ways to slice that cake, I think we're better off (for now) settling on an expressive enough IR and leaving it up to those implementing on top of the library to construct their own output configurations from the generated network layout IR.

\cc @tschuy @brianredbeard

Terraform output

Terraform output should be verified as working, and if not, fixed.

naming

The VPC/Subnet/AZ/etc naming should be clarified/made accurate.