Hi! I hope this is the right community to ask.
Next week I will be on the road for 5 Days for work. I have quite some spare time, so I thought I would dig up my raspberry project again and hopefully finish it.
I need it with me, because it controls some hardware, so a VPN to home does not work. So only option I could think of, is to connect the pi directly to my laptop via an ethernet cable. As far as I understood from some research is that I would need to install and run an DHCP server on my laptop, which they did not recommend. Alternatively they suggested to just take a router and plug both devices in there. I don’t really have a spare router, so that’s not an option either.
To be hones it confuses me a little, that there does not seem to be a standard for connecting to a device directly over a single cable and login with a user account.
Any recommendations how I can work on the pi like with ssh?
Thanks a lot!
Give each device a static address, and set the default gateway to whatever’s on the other end of the cable. You might need a crossover cable, but most NICs can work using a straight-through.
E.g. set the laptop’s address to
169.254.1.1/16and default gateway to169.254.1.2, and the RPi’s address to169.254.1.2/16and default gateway to169.254.1.1. They should be able to talk to each other then.If those addresses seem familiar - Windows uses the 169.254.0.0/16 subnet to automatically assign random addresses if DHCP fails, so that if there are several computers in the subnet, they’ll at least have addresses that can talk to each other. It’s called APIPA in Windows, and Zeroconf in the Unixverse.
You jump between 196 and 169 in your comment.It’s not just Windows that uses 169.254. That’s a special block used for self assigned link-local addresses.
oops, fixed. Caffeine withdrawal is hell.
Would you set a gateway? They’re on the same network.
Would the Pi automatically set an APIPA address if DHCP was not available? If so he need only connect the cable, and ask each machine what their address is.
No idea. It depends on what software it uses for network configuration, and how that software handles DHCP failure. I use NetworkManager and I’ve never gotten an APIPA address.
Thanks! That seems rather easy. Only thing I’m not sure about, I have basically only access to the pi over SSH. I could use a screen and keyboard but would prefer not to. What would happen if I configure the network wrong on the pi and can not connect anymore, even over my home network? Could I change the config by putting the SD card into my laptop and changing a file? Or is it possible to make it redundant, so if it can’t find a DHCP server, it automatically switches to the preconfigured settings you described? :) Thanks a lot
I’ve never used a pi, but it should be possible to mount the root partition and edit the
/etc/network/interfacesor/etc/dhcpcd.conffile, or/etc/NetworkManager/conf.d/*if you have NetworkManager (systemctl status NetworkManagerto check).You should also make sure that sshd is listening for connections from any address (
0.0.0.0and::).Network interfaces can be assigned multiple IP addresses. You should be able to use DHCP and a link local address at the same time.
That said I think this is easier to do with network manager. I’m not sure how it works with the rpi. But “link local address rpi” is a good search term to start with.
Configure ethernet with fixed IPs, and configure wifi to use your phone hotspot.
Then you can use one to troubleshoot the other as needed.
Then your normal setup would be wired between the pi+laptop, with the laptop connected to local wifi for internet.
Is there an easy method to know the self assigned IP address of the other machine if it’s run as headless?
The only methods I can think of is using something like Wireguard to see what IP addresses are talking, or ping all 32k IP addresses to see which responds.
The poster you’re replying to is suggesting a static IP, not an apipa up. You’d already know a static IP because you set it yourself.