Odd behaviour on em0 device in -stable ... I think ...

[Luigi Rizzo]

i am partly lost on the details of your specific question, but
the symptoms do seem to suggest a stale ARP entry, which must be
in the router (if the switch had a stale entry in its MAC forwarding
table, you would have problems even with local pings, not only
remote ones).

It is the OS that generates a gratuitous ARP every time you assign
an IP address (or alias) to a card, though i am not sure if it
sends one for each address assigned to the card, or just one for the
newly configured address -- the latter would not solve your problem.

	cheers
	luigi

On Sun, Jan 04, 2004 at 08:04:34PM -0400, Marc G. Fournier wrote:
> On Sun, 4 Jan 2004, Barney Wolff wrote:
> 
> > On Sun, Jan 04, 2004 at 04:31:41PM -0400, Marc G. Fournier wrote:
> > >
> > > The problem is that I want to move an IP from one of the other servers
> > > (all with fxp interfaces) over to the 4th, with the em device ... I -alias
> > > the IP from the fxp device, and alias it over to the em device, and I can
> > > no longer access it remotely ...
> > >
> > > If I alias it onto any of hte other two fxp based servers, it works fine.
> >
> > Something, either the switch or the router, has a stale arp table entry.
> > It's a little curious that this ever works, without resetting whatever
> > it is.  Perhaps the fxp's manage to send a gratuitous arp when taking
> > on a new alias.
> 
> re: gratuitous arp ... I was wondering if the nics do anything like this,
> but, shouldn't be 'ping -S <src ip> <dest ip>' not "force" something?
> Like, I could see remote pings not being able to find their way, but
> sourcing one of the IP in question to go out, I would have thought it
> would have found its way ...
> 
> Would the arp thing be nic based, or does the OS itself do it?
> 
> ----
> Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
> Email: scrappy at hub.org           Yahoo!: yscrappy              ICQ: 7615664
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