Does anybody know the default IP address of a S7-315-2 PN/DP CPU?... I cannot seem to find the information anywhere!

Thanks.

While the default address is 0.0.0.0, it may not be a good idea to keep using that when you connect other devices.

Also, to find out address of any device,  just use PLC>>Edit Ethernet Node in SIMATIC Step 7 software (assuming your PC is connected to the CPU via Ethernet). There is an option in the dialogue box that will search and discover all the S7 devices connected (and will also show their current IP addresses). 

Thanks....

Is there someway to change the IP address  WITHOUT Siemens programming software?

Hello,

yes you can use PRONETA or primary setup tool for this task.

Proneta: https://support.industry.siemens.com/cs/ww/en/view/67460624
PST: https://support.industry.siemens.com/cs/ww/en/view/19440762

Regards
Christoph