linux-kernel - Re: Why a host not ping-able?

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Date:	Tue, 04 Dec 2012 05:34:54 -0600
From:	Rob Landley <rob@...dley.net>
To:	Woody Wu <narkewoody@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Why a host not ping-able?

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--
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