If you want or need to directly hook up a second computer to your primary one via Ethernet cable, what is the easiest way to find the IP address for the second one? Today’s SuperUser Q&A post provides some helpful advice for a frustrated reader.
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
Photo courtesy of Keary O. (Flickr).
The Question
SuperUser reader Melebius wants to know how to find the IP address of a second computer directly connected to the first one by an Ethernet cable:
How do you find the IP address of a second computer directly connected to the first one by an Ethernet cable?
I can wait until Windows recognizes the other computer or scan IP addresses, but both actions take a long and unpredictable amount of time. Is there a faster way to recognize the second computer at the other end of the Ethernet cable connection? I have considered making a broadcast “Ethernet ping” and reverse ARP, but I have been unable to find any instructions for this technique.
The Answer
SuperUser contributor grawity has the answer for us:
Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.
Directly sending a name lookup (using nbtstat -a) might work (if it runs Windows and if you know the computer’s name).
The 169.254 auto-configuration involves sending some ARP probes with the host’s own address (you can see those in Wireshark).
“Ethernet ping” exists, but only works at the Ethernet level. It will not tell you anything about the IP (It is sometimes implemented in the NIC itself, but mostly not implemented at all).
“Reverse ARP” also exists, but is almost never actually implemented either. Its primary use was superseded by BOOTP and later DHCP.
