Re: How do I surely know I'm connected ?
At 01:02 PM 6/28/01 +0200, jfjoly@free.fr wrote:
>Hi,
>
>I'm looking for a sure way to know that a server is connected to Internet.
>Pinging may be a good way but what server should I ping to have a 100% good
results. If I ping yahoo.com (example), my server will be reported down as
yahoo.com is down (not so common, I admit). Is there a way to have a 100%
sure response ?
No. Because ANY other specific host may either be down or be unreachable due
to a routing problem between it and the Internet. (Actually, this reply
makes "the Internet" sound too well defined. The concept "connected to
Internet" is inherently imprecise -- ther is no "there" on the Internet to
be connected to, just a lot of specific routes (including alternate routes),
each of which either is or isn't working.)
Things you can do:
ping your gateway IP address. If you can't ping it, you aren't
"connected to Internet" by any reasonable definition. If you can ping it,
you still may not be connected (the gateway's outgoing connection may be
down ... this, unfortunately, isn't all that improbable).
ping some high-probability address. Your using yahoo.com is in that
spirit. Root names of big domains and the root DNS servers are other
possibilities (not good choices if you want to do this test every minute,
but OK if you want to do it by hand once a month).
--
------------------------------------"Never tell me the odds!"---
Ray Olszewski -- Han Solo
Palo Alto, CA ray@comarre.com
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