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Groups > linux.debian.user > #261532

Re: Debian 12 - IPv4 blocked without fail2ban & co

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On Wed, Sep 06, 2023 at 10:59:29AM +0200, Romain wrote:
> >
> > So when this is happening mtr works but http, ssh and ping don't?
> 
> Yes

I think there is definitely a firewall involved somewhere as that is
quite complicated selective blocking: it's allowing back the ICMP
Time Exceeded packets that mtr uses for telling the path to a
destination, but it's not allowing ICMP Echo Reply packets that ping
uses for getting a response, nor of course any of the TCP packets
for http, ssh, etc.

If it was a routing issue I'd expect total loss of all connectivity,
but you don't see that, and as you later mention, you can still
reach the destination from other hosts and even from other
subscribers to your home ISP.

The tcptraceroute may help you find out where this firewall lives,
but it may end at or just before where you'd expect your host to be.

You are absolutely certain that no firewall rules exist on your
server?

# itables -nL

and/or

# nft list ruleset

Cheers,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting

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Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-06 09:00 +0200
  Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-06 10:50 +0200
  Re: Debian 12 - IPv4 blocked without fail2ban & co Michel Verdier <mv524@free.fr> - 2023-09-06 10:50 +0200
  Re: Debian 12 - IPv4 blocked without fail2ban & co Andy Smith <andy@strugglers.net> - 2023-09-06 11:00 +0200
    Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-06 11:10 +0200
      Re: Debian 12 - IPv4 blocked without fail2ban & co Andy Smith <andy@strugglers.net> - 2023-09-06 15:30 +0200
        Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-06 15:40 +0200
          Re: Debian 12 - IPv4 blocked without fail2ban & co Paul van der Vlis <paul@vandervlis.nl> - 2023-09-07 10:00 +0200
            Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-07 10:40 +0200
  Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-07 09:40 +0200
    Re: Debian 12 - IPv4 blocked without fail2ban & co Max Nikulin <manikulin@gmail.com> - 2023-09-07 12:20 +0200
      Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-07 12:30 +0200
        Re: Debian 12 - IPv4 blocked without fail2ban & co Andy Smith <andy@strugglers.net> - 2023-09-07 12:40 +0200
          Re: Debian 12 - IPv4 blocked without fail2ban & co Max Nikulin <manikulin@gmail.com> - 2023-09-07 13:00 +0200
            Re: Debian 12 - IPv4 blocked without fail2ban & co zithro <slack@rabbit.lu> - 2023-09-07 14:20 +0200
              Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-07 23:50 +0200
                Re: Debian 12 - IPv4 blocked without fail2ban & co Max Nikulin <manikulin@gmail.com> - 2023-09-09 05:00 +0200
                Re: Debian 12 - IPv4 blocked without fail2ban & co Timothy M Butterworth <timothy.m.butterworth@gmail.com> - 2023-09-09 06:50 +0200
                Re: Debian 12 - IPv4 blocked without fail2ban & co Romain <romain@borezo.info> - 2023-09-09 10:40 +0200

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