From anyone who has taken any networking lessons, one of the early things taught is APIPA. Automatic Private IP Addressing (APIPA) is a feature of Windows systems. And also seen in other systems such as Linux. This handy feature automatically creates a IP address on an interface.
The tip I am sharing today is when you are stuck in situation where no DHCP server is available. Let’s say you hook a Ethernet cord up to a printer and your laptop. If your printer is set to DHCP, you can also set your laptop to DHCP. You both will then receive a APIPA address. The address will be in the 169.254.0.1-169.254.255.254 range.
Most technicians learn that APIPA is bad, yes it is because it points to issues with DHCP server. However the wonderful thing is that an IP address is automatically made by the device. Note this will be an IPv4 address, IPv6 is a different story. Now in the earlier example when you have two devices connected to each other, there is a possibility to communicate.
You don’t need to port scan to find the other device. Just open up Wireshark, disable your network interface, re-enable, and start monitoring it in Wireshark. You should start to see Arp responses from the other device, showing it’s APIPA address.
Below is an example I connected a new Raspberry Pi to my computer. And after following the steps above found the IP address to ssh into. I didn’t need to waste time, ip scanning, connecting a monitor and usb keyboard. Once connected I could then configure the network settings. A handy tip to keep in mind about APIPA.
