Communicating machines through cross-over cable?

José Perez
José Perez used Ask the Experts™
I hope someone can help me with this.

I have received a computer and a robotic machine (PC that connects to a Robotic machine through a cross over cable).
Currently, I have 2 issues:

1. I don't know what's the IP of the robotic machine (and really need to guess it)
2. I dont have any answer from the robotic machine, but I can see both are connected, and Lan ports appears properly connected (lights are flashing when connected each other)

So the question is, what can I do, or what commands can I launch to make the robotic machine to answer?
I know there are applications that scan networks and computers, easily, but you have to provide the subnet (ie. advanced ip scanner) or, at least, provide the ip of a target machine.
In this case, i don't have the ip of the robotic machine, i just have a computer connected to the machine via xover cable and I do know they are connected.

So, I would like, if you can tell or recommend, what can I do so the machine answers to the computer, either via Windows or Linux commands. Everything can work for me, I just need some answer from the robotic machine... probably from an answer I can extract the ip of the source machine.

Please, any idea can be usefull.
Thanks a lot.
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Distinguished Expert 2017
Cross means each side has to have a static ip, one option is to use wireshark or Ms network monitor tool to see what flows through through the channel.

There has to be some info identifying or the robotic device has to have a tool on the PC that helps it locate it on the network by way of the MAC address.

Open the application on the PC that supposed to control the robotic machine.  It could be that the PC needs to be turned on first and then the PC.

What is the IP address on the PC? If it is in the form of 169.254.x.x you are having an issue.

If it has a valid ip, in the format of 10.x.x.x 192.168.x.x or 172.16-31.x.x you should be fine.
Ping the broadcast addres (usually the last ip in the segment) if the robotic machine us configured to respond to pings, it will respond,....
bbaoIT Consultant
as mentioned, you better use a network sniffing utility to listen from the one end (A) of the crossover cable while the other end (B) is connected to the robotic machine. be aware that the end (A) doesn't need to be that PC you received, if due to any restrictions you can't install additional software such as Wireshark or MS Network Monitor on it. it can be any computer with proper utilities installed.

if for some reasons you are not able to run any network sniffing or monitoring software, but you do have a logging enabled router, you may simply use a CAT5/6 cable to connect the router's WAN port and the robotic machine. then from the LAN side of the router, log in to its web console, check the logs on WAN port and see if any traffic there.

also be aware that you are probably using a bad crossover cable which causes you see nothing from the robotic machine. make sure the cable is good.


Hi, after trying lot of things with xover cable (none of them work), I think something can result trying with "logging enabled router". Can you please suggest a cheaper one or recommend any model of this kind of router? Hopefully one than you have experience with.
Distinguished Expert 2017

when using a cross cable, before connecting it to a HUB or to the other system ,did you have a chance to install and run wireshark such that you can see whether the other side is requesting an IP (DHCPDiscover)?
Connect it to a router that allocates IPs via DHCP will if the system is configured to obtain via DHCP, it will be listed as a client.


Finally I connect both machines and use Wireshark, information came as magic!
Thanks a lot.

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