I have multiple VPC in my account and I created most of VPC using subnet or or subnet blocks.

I am exhausted with my range due to not optimizing the IP address properly and adding a wrong route of under a VPC. I got to know about this when I tried attempted to establish VPC peering between two different VPC of subnet. I got to know later that I can use CIDR range and as private address in aws to create VPC. Also I created a VPC with CIDR and it works.

How come aws can offer multiple IP range for private IP address to create VPC and multiple subnet under VPC? Can somebody help me to understand aws private IP range?

Is this something being virtual we can use any range of IP address as private address? How does this not affect connectivity from aws server to internet if we can choose any random CIDR as private IP address or there is some limit?

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closed as off-topic by HopelessN00b, ceejayoz, kasperd, Sven Apr 18 '16 at 17:00

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  • "Questions should demonstrate reasonable business information technology management practices. Questions that relate to unsupported hardware or software platforms or unmaintained environments may not be suitable for Server Fault - see the help center." – kasperd, Sven
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locked by Sven Apr 18 '16 at 17:03

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  • 3
    /8 covers 16 million IPs. /12 gives you over a million /16 covers 65 thousand. I doubt you've exhausted these ranges. – ceejayoz Apr 18 '16 at 13:51
  • 3
    Besides, I believe that a quick whois query for the ranges in question will prove interesting. – a CVn Apr 18 '16 at 13:53
  • 2 is a DoD Network. Not sure what you are doing but it can't be right. – Daniel Widrick Apr 18 '16 at 13:55
  • 3
    Everything bad you think will happen, will. If you use the 20.x.x.x range internally you will not be able to access off site 20.x.x.x resources. The rest of your question doesn't really make sense since the context is ridiculous. – Daniel Widrick Apr 18 '16 at 14:00
  • 3
    @PratapSingh No, it's not a flaw in AWS. It's a flaw in the person setting it up. AWS isn't in the business of stopping you from doing dumb things. I can confirm that VPC will let you set up any CIDR block (as long as it's /16 or smaller), but it's not a good idea to do so. Just like it's not a good idea to run your personal blog on one of their g2.8xlarge instances, but you can. – ceejayoz Apr 18 '16 at 14:05