Subject: Re: [vserver] ping vs. IP address vs. MAC (address)
From: Martin <inkubus@interalpha.co.uk>
Date: Fri, 01 May 2009 17:03:47 +0100

On Fri, 2009-05-01 at 08:54 -0700, Roderick A. Anderson wrote:
> I'm asking for a clue stick here.  First time I've run into this issue 
> ... hard.  Be a few times where it took a bit for outbound traffic to 
> get a route but can't remember running into this problem.
> 
> The short question is: does the network/NIC _know_ which IP address it 
> is responding for when a ping request comes in or does it just respond 
> to the ping request at the MAC (hardware?) level?
> 

Ping uses ICMP, which is a service running over IP, thus it is processed
with the rest of the IP layer (in the kernel, unless you ahve a very
expensive TCP/IP offload engine).  This is layer 3, MAC is a link level
(level 2) concept and thus independant of the processing of ICMP, beyond
providing a packet connection.

Cheers,
 - Martin