<p>AWS docs show what the reserved IP's in each subnet are: <a href="https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html</a></p>
<p>The gist of it is, the first 4 IP's and the last IP of the subnet are off limits if your subnet starts with the same IP as the VPC.  It's probably a good rule of thumb to avoid assuming these IPs are going to be available in any subnet even though potentially the second subnet address reserved for DNS could be available for consumption in another subnet. A better rule of thumb to avoid under-sizing subnets in AWS. Like, never plan on using a subnet smaller than /24. You need them for auto-scaling groups, NAT gateways, VPN's, and networking hooks into other apps like DynamoDB or Lambda.</p>

CC BY-SA 4.0
2021-05-26T14:52:41.887Z
2021-05-26T14:52:41.887Z
Peter Turner
<p>Is there a way to find how many total ip addresses that an AWS subnet can hold?</p>
<p>If my subnet CIDR is a.b.c.d/n, then the total ips allowed in this subnet - are they decided by a, b, c &amp; d as well?</p>

<amazon-web-services>
How to find the total ips allowed by an AWS subnet?
Biju
# How to find the total ips allowed by an AWS subnet?

(Asked by: username_0 on 2021-05-26)

Is there a way to find how many total ip addresses that an AWS subnet can hold?

If my subnet CIDR is a.b.c.d/n, then the total ips allowed in this subnet - are they decided by a, b, c & d as well?

**Tags:** amazon-web-services


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## 1 answers

### Answer by username_1 on 2021-05-26. Score: 1

AWS docs show what the reserved IP's in each subnet are: <https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html>

The gist of it is, the first 4 IP's and the last IP of the subnet are off limits if your subnet starts with the same IP as the VPC. It's probably a good rule of thumb to avoid assuming these IPs are going to be available in any subnet even though potentially the second subnet address reserved for DNS could be available for consumption in another subnet. A better rule of thumb to avoid under-sizing subnets in AWS. Like, never plan on using a subnet smaller than /24. You need them for auto-scaling groups, NAT gateways, VPN's, and networking hooks into other apps like DynamoDB or Lambda.


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