[Gllug] Pinging a machine that is down

[Robert McKay]

On 1/9/10, Alain Williams <addw at phcomp.co.uk> wrote:
> I have just rebooted a customer's machine (to run a new kernel).
>
> I left a ping running so that I could login once it had rebooted.
>
> I noticed that the ''Destination Host Unreachable'' appear in 3s with the
> one before
> the first of the 3 missing. Eg in the sequence below 100,101,102 all appear
> at once,
> there is then a pause before 104,105,106 appear.
>
> Anyone any idea why it behaves like that ?

Not really, but maybe some combination of overlapping caching/probing
of the route phasing in and out of sync at different levels/hops.

You've got the gateway to your host.. it's going to be arp'ing for the
host.. but it will probably wait for a while before deciding that it
isn't going to get a reply (possibly allowing multiple ping packets to
queue up) it may then also cache the fact that it didn't get a reply
for a little while.

Rob.
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