Siemens S7-1200 System Manual page 164

Device configuration
5.7 Configuring the CPU for communication
The MAC address is printed on the front, lower-left corner of the CPU. Note that you have to
lift the lower door to see the MAC address information.
①
Initially, the CPU has no IP address, only a factory-installed MAC address. PROFINET
communications requires that all devices be assigned a unique IP address.
164
MAC address
Use the CPU "Download to
device" function and the
"Extended download to device"
dialog to show all accessible
network devices and ensure that
unique IP addresses have been
assigned to all devices. This
dialog displays all accessible and
available devices with their
assigned MAC or IP addresses.
MAC addresses are all-important
in identifying devices that are
missing the required unique IP
address.
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG