From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752790Ab2LDLe7 (ORCPT ); Tue, 4 Dec 2012 06:34:59 -0500 Received: from mail-oa0-f46.google.com ([209.85.219.46]:52528 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751807Ab2LDLe6 convert rfc822-to-8bit (ORCPT ); Tue, 4 Dec 2012 06:34:58 -0500 Date: Tue, 04 Dec 2012 05:34:54 -0600 From: Rob Landley Subject: Re: Why a host not ping-able? To: Woody Wu Cc: linux-kernel@vger.kernel.org In-Reply-To: (from narkewoody@gmail.com on Tue Dec 4 00:17:25 2012) X-Mailer: Balsa 2.4.11 Message-Id: <1354620894.27682.5@driftwood> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; DelSp=Yes; Format=Flowed Content-Disposition: inline Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/04/2012 12:17:25 AM, Woody Wu wrote: > Hi, list > > I am not sure this has something with kernel. It doesn't. > But the system I just > generated cannot be reached from ping. It can ping outside, but if I > ping it from outside, I just get "Destination Host Unreachable". Some distributions' default firewall rules respond to icmp packets with a host unreachable packet. This is a system/network administration thing (iptables) and nothing to do with kernel development. > I think there is not firewall in between, There's a firewall built into linux, read the man page for the "iptables" command. The "iptables-save" command dumps your entire current ruleset to stdout so you can see what's in there. (You might have to run it as root, I forget.) https://help.ubuntu.com/community/IptablesHowTo Rob