Re: [tlug] Ping vs www server

[Scott Robbins <scottro@example.com>]

On Fri, Apr 11, 2008 at 04:29:01AM +0900, Stephen J. Turnbull wrote:
> Scott Robbins writes:
> 
> 
> Actually, what ping tests is whether the domain implements the
> Internet ICMP echo protocol.  This *usually* is equivalent to physical
> connectivity, but not always.  Try pinging turnbull.sk.tsukuba.ac.jp,
> then browsing http://turnbull.sk.tsukuba.ac.jp/.

Yes, I was simplifying.  My own scottro.net won't respond to pings
either.  

However, to the OP, Stephen is correct.  (You'll find that he usually is
about such things.)  Many people will now block ping requests.

In the example you mention, though, my explanation, though sloppy, was
more or less accurate.  The fact that you can ping it indicates the
machine is physically up and running, but since you can't reach it
with http on port 80, that does mean that for whatever reason, it's not
accepting http connections on port 80---this could mean the we bserver
programs are down, that they've blocked it, etc., etc. 

> 
> BTW, there are ping (fping, maybe?) and traceroute (tcptraceroute)
> tools that can be used to check whether a given host is responding via
> TCP as well as the lower-level ICMP.

Right now, my head is so full of monitoring tools I don't want to think
about it.  (For the last few weeks, I've been making proof of concept
cacti and nagios setups.) 

> 

-- 
Scott Robbins
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