[GRLUG] question about ping

[Bill Littlejohn]

 I was thinking that may be the case, but I wasn't at all sure.
Thank you.
-Bill

On Thu, Mar 3, 2011 at 2:35 PM, Michael Mol <mikemol at gmail.com> wrote:

> "Destination Host Unreachable" is an ICMP response for IP packets when
> a router can't find a way to get the packet nearer to its destination.
>
> These response packets may be filtered out by some network's
> firewalls, in which case you might not hear anything back. If the
> packet is passed on to the next router, and the next router never sees
> it (or glitches in some other way), you may not hear anything back. If
> the packet reaches the target host, but the target host is configured
> to not send ICMP ECHO replies, you won't hear anything back.
>
> I've also dealt with at least one system where the firewall was
> configured to send an ICMP destination host unreachable response in
> the case of a filtered port, rather than sending RST or silently
> dropping the packet. _That_ one was puzzling.
>
> On Thu, Mar 3, 2011 at 2:29 PM, Bill Littlejohn <billl at mtd-inc.com> wrote:
> > When I ping some non-existent IP addresses I get Destination Host
> > Unreachable, and some others return nothing.
> > What's actually the difference?
> >
> > billl at MTD-IT-ADM2:~$ ping 192.168.1.113
> > PING 192.168.1.113 (192.168.1.113) 56(84) bytes of data.
> > From 192.168.1.210 icmp_seq=2 Destination Host Unreachable
> > From 192.168.1.210 icmp_seq=3 Destination Host Unreachable
> > From 192.168.1.210 icmp_seq=4 Destination Host Unreachable
> > From 192.168.1.210 icmp_seq=5 Destination Host Unreachable
> > From 192.168.1.210 icmp_seq=6 Destination Host Unreachable
> > From 192.168.1.210 icmp_seq=7 Destination Host Unreachable
> > ^C
> > --- 192.168.1.113 ping statistics ---
> > 8 packets transmitted, 0 received, +6 errors, 100% packet loss, time
> 7017ms
> > , pipe 3
> > billl at MTD-IT-ADM2:~$ ping 192.168.1.7
> > PING 192.168.1.7 (192.168.1.7) 56(84) bytes of data.
> > ^C
> > --- 192.168.1.7 ping statistics ---
> > 17 packets transmitted, 0 received, 100% packet loss, time 15999ms
> >
> >
> >
> > --
> > This message has been scanned for viruses and
> > dangerous content by MailScanner, and is
> > believed to be clean.
> > _______________________________________________
> > grlug mailing list
> > grlug at grlug.org
> > http://shinobu.grlug.org/cgi-bin/mailman/listinfo/grlug
> >
>
>
>
> --
> :wq
>
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
>
> _______________________________________________
> grlug mailing list
> grlug at grlug.org
> http://shinobu.grlug.org/cgi-bin/mailman/listinfo/grlug
>

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://shinobu.grlug.org/pipermail/grlug/attachments/20110303/8af8879b/attachment-0001.html>