How to modify the IP address range of my VPC or subnet by Raj Gupta

The CIDR block that you add when you create the VPC cannot be changed, but you can add and remove secondary CIDR blocks to change the IP address range of the VPC.

To add secondary CIDR blocks for your VPC :

1. Open the Amazon VPC console.
2. Select Your VPC.
3. Go to the Action and click on edit CIDRs.
4. Then click on  ADD IPv4 CIDRs then add the IP range you want to add save it.

You cannot change the IP address range of a VPC subnet after you create that subnet. You must instead create a new VPC subnet with your desired IP address range.

Important: Before you delete a subnet, be sure to create Amazon Machine Images or snapshots of existing resources as necessary, and then delete all the underlying resources in the subnet.