Re: ssh/ping only works to some systems, not including mine unfortunately
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/
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