Re: [vserver] ping vs. IP address vs. MAC (address)

From: John A. Sullivan III <jsullivan_at_opensourcedevel.com>
Date: Fri 01 May 2009 - 17:38:19 BST
Message-Id: <1241195899.6353.43.camel@jaspav.missionsit.net.missionsit.net>

On Fri, 2009-05-01 at 09:27 -0700, Roderick A. Anderson wrote:
> Michael S. Zick wrote:
> > On Fri May 1 2009, Martin wrote:
> >> 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?
> >>>
> >
> > The *NIC* responds to MAC address(es) -
> > The *network* - now that is a big question. ;)
>
> So if a ping request comes in the NIC it should respond regardless of
> what IP it was sent to. That makes sense.
The NIC will respond but the IP stack will not
>
> >
> > There is a ARP cache in the kernel, but it *should* be rather short-lived.
> > Try arpping to help find out what is happening.
>
> Oddest stuff happening. When I check the arp table on the old host the
> troublesome guest's name (not IP) doesn't show up. When I ping the
> guest from another system the entry shows up.
>
> I was thinking the main router, between the two hosts, is using a long
> lived arp cache.
I have seen routers hold onto ARP cache for a very long time.
>
> I prefer staying way from it, the router, but may have to get access and
> take a look around. Maybe flush the arp cache, if I can, right after
> shutting down the old guest and starting the new.
>
> Thanks for the ideas.
>
>
> \\||/
> Rod

-- 
John A. Sullivan III
Open Source Development Corporation
+1 207-985-7880
jsullivan@opensourcedevel.com
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Received on Fri May 1 17:44:55 2009
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