If you need to install an SSL certificate and private key on multiple servers you should generate a CSR from the first machine and install the issued SSL certificate on that machine. Once installed on the first machine you should make a backup of your private key and SSL certificate and import it to machine #2, and so on. So, you will only be generating one CSR and using the same keys for each machine. If you are working with Windows IIS servers this is an easy task.
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