Forum Discussion
Using ASR to Migrate servers to the same subnet
I'm afraid Eric is right...
You won't be able to use the same subnet (layer 2 connectivity) natively with Azure, even with ExpressRoute for example, without the help of some third party solution.
Another way you could look at this is to redesign the network architecture around the application that requires the same IP.
Depending on how clients connects to the app, you could for example create a new address space with the same ip subnet in Azure, but not connect it back to your on-premises network and instead get the client to access the application through a public endpoint. I realise there are many factors to be considered such as performance, security, etc. but this is only an example to get you thinking about different approaches to the problem if you can't get the layer 2 connectivity going in Azure.
Cheers,
Stephane