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Troubleshooting • Re: Point-to-point ethernet - Unidentified Network - headless debian bookworm

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Something Murph9000 didn't mention or didn't spot: using google's public DNS servers on a point to point link like this simply won't work. Even if those machines can reach them via a different route/interface the servers won't know anything about that link or your internal network. It may also cause problems with name resolution on internal connections that use other interfaces too.

Some further tips to add to what I wrote in the sticky:
  • This stuff is much easier to debug when you have a way into both machines that does not rely on the network link in question.
  • Make sure there is only one connection for that interface in NM. If there are more than one, it may be using the wrong one.
  • Use a private subnet that does not conflict with any other subnet the devices are connected to.
  • As suggested by Murph9000 you could use the link local/mdns self assigned subnet (169.254.0.0/16) for the static IP on the Pi though there may be a tiny chance of a conflict with what the PC assigns to itself.
    If you go that route setting the PC end back to automatic should "just work".
  • Do not specify a gateway unless the machine listed is acting as an internet gateway.
  • Do not set a DNS server unless the machine(s) listed are running one and at least one of them is one the same point to point link.
  • If either machine can reach the other via multiple paths (e.g WiFi and the ptp link) use IP addresses not hostnames. Hostnames might not resolve the way you think they should.
I'm also curious. How did you connect over ssh to configure networking on the Pi? Is there a different link that both devices are connected to? If not, and the ptp link was working why did you change it?

As I suggested in the stickied thread, I'd go old school and use /etc/network/interfaces (or a file in /etc/network/interfaces.d). That bypasses NM entirely on that interface so you don't have to deal with potential conflicts etc. At least ti does on RPiOS.

(To the old hands, I am not using PTP/ptp to indicate use of the Point to Point Protocol. Which should be obvious as the usual abbreviation for that is PPP.)

Statistics: Posted by thagrol — Sun Sep 29, 2024 1:11 am



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