On Wed, Jan 22, 2025 at 01:29:41PM +0000, Chris Green wrote: > I have a remote headless system (running bullseye, will be updating to > bookworm when I'm next there) that can connect to some systems using > ssh but not to others (to which I can connect from everywhere else). > > It also can't ping the systems which it can't connect ssh to. > > I can't see any pattern in the systems to which it can connect or > those which it can't connect to. It's connected via 4G so it's > CGNATted. I connect to it (using ssh) via a remote ssh tunnel that it > sets up when booted. > > It gets the correct IP address for all 'my' systems that run an ssh > server and I can cannect to all these systems from my home desktop and > laptop machines using ssh. > > Does anyone have any ideas on how to diagnose its failure to connect > to all of 'my' systems.
How many network interfaces have you got ? I suspect one (+ loopback). What do you get when you run traceroute to something that you cannot connect to ? What are your routing tables ? Do you have a firewall ? Is it an IPv4/IPv6 thing ? So that you can connect to systems over IPv4 but not IPv6 ? Run: host machine-that-you-can-ping host machine-that-you-cannot-ping Then try to ping the IPv4 and IPv6 addresses. -- Alain Williams Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer. +44 (0) 787 668 0256 https://www.phcomp.co.uk/ Parliament Hill Computers. Registration Information: https://www.phcomp.co.uk/Contact.html #include <std_disclaimer.h>
