Can't connect to a machine through ethernet together with a set up wi-fi connection

[Guillaume Cuffel]

Hello there,

I'm not an network admin so my worry is probably dumb to solve, but if it's the case, that would be great

For my project, I deployed some mini PCs that are all connected to the same router by Wi-fi to be able to synchronize their internal clock. These mini PCs don't have a direct monitor to access it, so what I do to control one of them is using another laptop and connect it to the same Wi-fi network thanks to a VNC client (vino & remmina).

That's working pretty well most of the time, but sometimes it is not when a mini PC is a little bit to far from the router. To solve that problem, I though I would only use a single Ethernet cable and directly plug it from the laptop to the mini PC and set a fix IP on a specific interface (eth0). In that case, the direct connection works, but I can't ping the wi-fi network anymore...

Do you know if what I want to do is possible? Otherwise, do you have another idea to solve that issue?

Thank you very much for yous answers

PS: every single machine is running under Ubuntu 16.04

 

[atanere]

That's working pretty well most of the time, but sometimes it is not when a mini PC is a little bit to far from the router. To solve that problem, I though I would only use a single Ethernet cable and directly plug it from the laptop to the mini PC and set a fix IP on a specific interface (eth0). In that case, the direct connection works, but I can't ping the wi-fi network anymore...

Welcome to the forums!

Maybe I'm not understanding correctly. And my networking skills were never very good either. But if your mini-PC is out-of-range from the wireless network, then how could a wireless ping possibly work? This would just be a range problem and you would need to move the mini-PC closer to the other devices. I don't see how manually assigning a fixed IP address helps you as long as the DHCP assigned address from the router has not expired. (But if manually assigning an IP address, also be sure to check the subnet mask, default gateway, etc.)

When you say "the direct connection works" (from laptop to mini-PC, on ethernet).... do you mean it can reach the router and the Internet? You did not say that the mini-PC is connected by ethernet to the router, so if you are able to reach the router and Internet, then you are doing so by wireless... in which case you should also be able to ping your router at least.

Again, sorry if I am not understanding correctly.

 

[rstanley]

Don't assign a static up to either your WiFi or ethernet port. Use dhcp for both.

As long as the laptop is within range of the router, both connections should work together. If not then you have some other issue.


This setup works fine on my Lenovo laptop.

 

[Guillaume Cuffel]

Thank you very much for your rapid answers, I found the solution and you were actually both right. The mistake was setting up a bad gateway address in my /etc/network/interfaces. I removed it and it worked fine.

"Don't assign a static up to either your WiFi or ethernet port. Use dhcp for both."
I prefer fixing IPs because this is a closed network not likely to evolve very often. Like that, I can easily connect by VNC knowing who each IP belongs to.

Thanks again,
Guillaume

 

[rstanley]

You stated in the OP:

I would only use a single Ethernet cable and directly plug it from the laptop to the mini PC and set a fix IP on a specific interface (eth0).

Using static IP's are fine, but I would use static IP addressing through the dhcp system rather than manually fixing the IP address on the NIC itself. Much easier to maintain when you have multiple devices.

I say this not only for you, but for the benefit of others reading this thread.