I'm asked to update our current aws vpc environment, our current vpc cidr is 172.30.0.0/24, below are subnets and avilability zones:

• 172.30.0.0/26 - public1 - az1
• 172.30.0.128/26 - private1 - az1
• 172.30.0.64/26 - public2 - az2
• 172.30.0.192/26 - private2 - az3

I'm not able to recreate the vpc because some other services have been deployed to them, as you can see, in az2 and az3, there are only one subnet, and I want to add one subnet in az2 and az3

But I don't know how can I split it, could you please give some idea

CodePudding user response：

can I use 172.30.1.64/26 for new subnet at az2

Sadly, you can't, as your VPC cidr is 172.30.0.0/24. Since you can't delete any of your current subnets, I think the best way is to add new cidr to your VPC. You can add 172.30.1.0/24, and then you will be able to create 172.30.1.64/26 subnet.

CodePudding user response：

Using a CIDR calculator:

Your VPC 172.30.0.0/24 goes from 172.30.0.0 to 172.30.0.255:

• Subnet 172.30.0.0/26 goes from 172.30.0.0 to 172.30.0.63
• Subnet 172.30.0.64/26 goes from 172.30.0.64 to 173.30.0.127
• Subnet 172.30.0.128/26 goes from 172.30.0.128 to 173.30.0.191
• Subnet 172.30.0.192/26 goes from 172.30.0.192 to 173.30.0.255

Therefore, the VPC range is full!