Hey René,
you missed something in the command syntax. After I have read your lesson, I tried the example. With the shown syntax John still doesn’t advertise the Loopback addresses and the connected network. You probably wrote it in the lesson, but I had to complete:
John(config)#router eigrp 12
John(config-router)#redistribute rip
John(config-router)#redistribute connected
John(config)#router rip
John(config-router)#redistribute eigrp 12
John(config-router)#redistribute connected
With this syntax, John started to advertise the Loopback and his directly connected networks. I hope it’s no mistake from my side.
Have a good one!