Hey!
I'm using NeptuneOS 6.5 on 3 machines.
Today I've noticed that I can't ping these machines. And no: no iptables rules, policy is ACCEPT.

I can ssh into these machines. Other services like VNC are reachble, too.

With tcpdump I can see incoming icmp echo requests. But no answers from the machine.

This goes as far as I even can't ping 127.0.0.1 from inside! The machine also can't ping its own IPs on its interfaces.
I've been using Linux/Debian (desktop and server) for over 15 years now. But this is weird.

And it's reproducible on 3 maschines!

So is this a new "security feature" that I've missed?
Or a bug?

Regards
Ralf

    thanks for the reply.
    But, no, iptbale is not my issue. As I said. On all 3 machine, I have no iptables rules.

    And yes: one machine (Laptop) was startet from the scratch (turned on) and the problem is
    instantly present.

    And it's not only localhost. I can't ping ANY interface. Neither from inside or from outside.
    On all 3 PCs.

    I guess it could be a kernel bug or something.The PCs get the echo request but jsut don't answer them.
    I see no answers in tcpdump.

    ralf Could be that we or debian protects this via sysctl rules. Check the config files in /etc/sysctl.d/*.conf files to see if there is a config blocking this.

        you got it!!

        in /etc/sysctl.d/neptune.conf 😀
        neptune.conf:net.ipv4.icmp_echo_ignore_all=1

        Why is that?

        Sorry guys, but for as a network admin this is a bug!

        Why block icmp?

        Ok, I'll take this out and test ist on my third machine which I can reboot without problems.

        But I would suggest to remove this in the next Neptune release please.

        Thanks.

          The ping ignore is in the net speed tweak section. But I don't think blocking icmp echo requests will speed up your system ;-)

            Yeah .... It works! Test ok on 3rd machine. 😄

              Great. I think we deactivated for security reasons. There were some security issues related to it at one point when we created the config.
              I will take a look into it and it will be removed for Neptune 7

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