You can use the same key combination on all servers. No need to create a seperate key for every machine. I use the same key and key.pub combination on several servers. Copy the .pub key to the destination servers and add it to authorized_keys, copy the key itself to the server from which you want to connect and you're done. You can then connect using the same key from any server where you saved it to any server where you added the .pub part. Of course, for security's sake you need to be aware that if someone gets their hands on your key, they'll have access to all your servers, so take some extra precautions.