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I have a VPC, and when I click "Edit CIDRs" I see this:

enter image description here

...which looks great, 10.1.0.0/16 is exactly what I want for the CIDR block. However, when I add a new subnet to this VPC the route table for the subnet is automatically setup like this:

enter image description here

Note that's a 10.0 local route instead of the desired 10.1. I have no idea how that found its way into our VPC but I cannot figure out a way to remove it (it's not removable when I click the "Edit" button on the top left in the screenshot), and if I can't I think my only option is to recreate the VPC which is going to be a major undertaking.

Is it possible to remove that route? I don't understand why it's not listed on the "Edit CIDRs" dialog if it's automatically going to be associated with any new subnets I create.

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  • Hi What subnet did you add into the VPC? – Michael Brown Mar 8 '17 at 19:31
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This entry is there because you have enabled ClassicLink for this VPC. The entry is correct, and it can't be removed, other than by disabling ClassicLink. This is the supernet for the private IP addresses in EC2-Classic.

When you enable a VPC for ClassicLink, a static route is added to all of the VPC route tables with a destination of 10.0.0.0/8 and a target of local. This allows communication between instances in the VPC and any EC2-Classic instances that are then linked to the VPC. If you add a custom route table to a ClassicLink-enabled VPC, a static route is automatically added with a destination of 10.0.0.0/8 and a target of local. When you disable ClassicLink for a VPC, this route is automatically deleted in all of the VPC route tables.

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/vpc-classiclink.html#classiclink-basics

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  • That's fantastic news since we no longer require ClassicLink. Many thanks! – Madbreaks Mar 8 '17 at 21:01

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