I've been trying to connect to my raspberry pi without interface. Even this wasn't too helpful because I can't locate its ip_addr. Thank you.
If the RPi is on your network, you can use nmap to find out which IP address it has.
If you have DHCP enabled, you can check your router. Or just test your entire network for devices, using nmap 192.168.x.0/24 (replacing 192.168.x by your network address).
You can also buy a serial console cable and connect via COM.