Re: Arp a problem?

To: Ard van Breemen <ard@xxxxxxxxxxxxxxx>
Subject: Re: Arp a problem?
Cc: Joseph Mack <mack.joseph@xxxxxxxxxxxxxxx>, lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Joseph Mack <mack.joseph@xxxxxxx>
Date: Mon, 30 Oct 2000 08:08:19 -0500
Ard van Breemen wrote:

> Yep. But I could not find it in the howto... And the solution
> was really simple...

glad you figured it out.

there was a strong vote at the time I wrote that section to exclude 
the router as part of the LVS. Of course if you have access to the router 
then life is a lot simpler and you may as well take advantage of it. 
I'm going to include this info in the next iteration of the HOWTO,

> > This is one of the ways of handling the arp problem. Some people do not
> > have access to the router. When you fail-out a director, the MAC address of
> > the VIP changes. Check that the entry in the router gets flushed.

> Well, what really seems to help is to set the arp timeout values rather
> high on the router, and let the new director broadcast unsolicitied
> arp's (arping -U dip) for the dip. In our production set-up (not
> load balanced, and fail-over by aliasing the IP's and upping it
> and broadcasting the arps) this is common practice. After the first arp,
> the router knows the new mac of the dip.

some routers will ignore these and you're stuck with the old MAC (security

> And yes, we do have access to the router :)...


Joseph Mack PhD, Senior Systems Engineer, Lockheed Martin
contractor to the National Environmental Supercomputer Center, 
mailto:mack.joseph@xxxxxxx ph# 919-541-0007, RTP, NC, USA

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