[Linux-Biella] kernel: neighbour table overflow

[Paolo Ciarrocchi]

On Thu, 24 Feb 2005 14:48:22 +0100, Fiorenza Meini <fmeini a robinson.it> wrote:
> Ciao a tutti,
> cosa significa un errore del genere sul un sistema linux?
> Ho un server che lavora per qualche ora, poi non riesce ad effettuare più nessuna connessione dando l'errore "no buffer space". Nel file di log viene visualizzato l'errore che ho riportato nel soggetto del messaggio.
> 
> ..aiuto..


From: David S. Miller <davem a davemloft.net>
To: Dominik Karall <dominik.karall a gmx.net>
Cc: earny a net4u.de, linux-kernel a vger.kernel.org
Date: Tue, 26 Oct 2004 16:06:42 -0700
Subject: Re: Neighbour table overflow.
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On Wed, 27 Oct 2004 00:11:26 +0200

- Hide quoted text -
Dominik Karall <dominik.karall a gmx.net> wrote:

> On Tuesday 26 October 2004 23:52, Ernst Herzberg wrote:
> > On Tuesday 26 October 2004 19:39, Dominik Karall wrote:
> > > can anybody explain why i get thousands of "Neighbour table overflow."
> > > messages? i didn't get such ones with older kernels (~2.6.6).
> >
> > Do you set a default gateway?
>
> yes, default gateway is set to our server.

From: David S. Miller <davem a davemloft.net>
To: Dominik Karall <dominik.karall a gmx.net>
Cc: earny a net4u.de, linux-kernel a vger.kernel.org
Date: Tue, 26 Oct 2004 16:06:42 -0700
Subject: Re: Neighbour table overflow.

Do you use a large subnet mask?  For example /16 or /8 or
something like that?

If so, you will need to bump up the neighbour table garbage
collection thresholds under /proc/sys/net/ipv4/neight/default/
Specifically gc_thresh1, gc_thresh2, and gc_thresh3

You probably have a huge number of machines on your subnet


Oppure

You may also be the 'victim' of a poorly configured router.

Out-of-the box, Cisco routers come with proxy ARP enabled;
they will reply to ARP requests for any IP they can route,
that isn't routed via the interface they receive an ARP
request on.  This makes them more 'plug-and-playful' for
equipment that talks IP, but doesn't understand routing
(assuming any still exists).

Check the output of
 arp -an
and see if there isn't a single MAC accounting for the lion's
share of your ARP cache.  If there is, seek and destroy^H^H^H^H^Hfang


-- 
Paolo <paolo dot ciarrocchi at gmail dot com>
msn: paolo407 a hotmail.com
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