Re: arp cache incomplete entries

[Celejar <celejar@gmail.com>]

On Thu, 11 Oct 2012 16:33:13 -0400
staticsafe <me@staticsafe.ca> wrote:

> On 11/10/2012 4:24 PM, Panayiotis Karabassis wrote:
> > Hi,
> >
> > I've noticed that, often, after establishing a connection to the local
> > network, important entries in the ARP cache, such as that of my
> > nameserver, appear as 'incomplete' and have not an associated hardware
> > address. Connection to these hosts often fails.
> >
> > What are the possible reasons why this could happen? And is there any
> > way to repopulate the ARP cache without reconnecting? How is the ARP
> > cache populated in the first place?
> >
> > Unfortunately, I often have to reset my router, and hence LAN
> > connections, because of problems with my ISP, so this problem appears
> > frequently.
> >
> > Thanks,
> > Panayiotis
> >
> >
> 
> Your router usually is the one doing ARP requests (correct me please if 
> I'm wrong) in the format:
> 
> "Who has x.x.x.x? Tell x.x.x.x"
> with a response of
> "x.x.x.x is $macaddress"

I'm no expert, but my impression is that any machine which is asked to
connect to some other host by IP address will issue such an ARP
request, so if I do 'ping x.x.x.x', and x.x.x.x has not been recently
in contact with my machine, my machine will issue an ARP request.

Celejar