Sunday, May 6, 2012

Amazon Web Services Public IPs

Last week, Amazon Web Services (AWS) expanded its list of public IP ranges in all of its US datacenters (regions in AWS). Looking at the available public IP (Elastic IP in AWS terms) ranges, one can make a simple calculation to arrive at the total number of public IP addresses that AWS has. Subtracting the network bits from 32 and raise 2 to that power. Subtract 2 from the result for network and broadcast addresses. For example, a "/19" network has 2 ^ (32-19) - 2 = 8190 unique IP addresses. In other words 8190 hosts can be setup in that network. Here is a list expanded to all the public IP ranges that AWS:

EC2 IP Addresses

If you sum it up, there are 1982384 public IP addresses with AWS across all of its datacenters. That's close to 2 Million public IP addresses. These IP addresses, apart from available to customers as Elastic IP addresses, could be used by AWS itself for various of its services such as Elastic Load Balancer, Route 53. Hence the number of servers that AWS datacenter has could be far less than this. There is an interesting article that tries to estimate the total number of servers through a different approach.

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