CPU315 (6ES7315-1AF01-0AB0)

I would say this is no problem, even with an AF01 CPU of the 315-2 series. I have a CPU 315-2AG10 and have two CP 343-1 connected to it and both have full network access.

The only thing to care about for you would be how may S7 resources are being used at this moment. The CP requires sometimes one and in case of FMS even sometimes two S7 resources. If you have no further free resources available it may lead into problems to run all functions.

To check the S7 resources you may have to enter the CPU Module Information and check the Communication tab. There you see S7 communication resources are in use. In your case there may be not more than2.

Best regards