s7-300 upload with unknown ip address

is it possible to upload the program as back of the s7-300 plc with unknown ip address?
Thank you..

1.Install Wireshark or Wireshark portable (http://portableapps.com/node/14304)
2.start Wireshark
3.set Wireshark filter to 'ARP'
4.reboot PLC and wait

In Step7 manager, use 'Find accessible nodes'.

Or use Primer setup tool to detect IP of this plc.

Just start the Upload Station to PG.
When prompted for the connection details, specify rack=0, slot=2, and use the "view" button to search for reachable stations.
When the CPU in question appears either by the IP or MAC address, then select it and start the upload (*).

*: When you see the IP address after searching but before upload, you can check if the CPUs IP is in your PCs IP range.
If not you have to change your PCs IP to mach before starting the upload.