Accessing Recovered Server with Direct Connect in Disaster Recovery Scenario with Same Private IP

Question

I have a setup where:

I use AWS Direct Connect to connect my on-premises network to the A region.

Server in A region with a private IP is replicated to the B region using Elastic Disaster Recovery (EDR).

In a disaster scenario the server in B region must come online with the same private IP as the original server in A region.

My concern is how I can ensure connectivity from my on premises network to the B region server (with the same private IP) via Direct Connect during a disaster, considering the same CIDR block is used in both regions (I can't attach B region's Virtual Private Gateway to Direct Connect Gateway due to IP block overlap).

Could you advise if there’s a supported AWS solution for this use case or suggest an alternative approach?

Brettski · Answer

The short answer to the question "how do I connect two networks with the same CIDR range" is "with great difficulty". In general, I'd recommend that you don't do that at all and find a way to architect your solution so that you don't have to do that. In the long run it will be far easier, far less maintenance and far less cost.

That said, there are things that you can do (and AWS services that can help) but given the nature of how IP addressing works, nothing here is perfect - every solution that you can think of has caveats. For further reading: https://aws.amazon.com/blogs/networking-and-content-delivery/connecting-networks-with-overlapping-ip-ranges/

Accessing Recovered Server with Direct Connect in Disaster Recovery Scenario with Same Private IP

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