[130022] in North American Network Operators' Group
Re: large icmp packet issue
daemon@ATHENA.MIT.EDU (fedora fedora)
Sat Sep 25 23:33:45 2010
In-Reply-To: <201009260318.o8Q3I7Cb029792@mail.r-bonomi.com>
Date: Sat, 25 Sep 2010 22:33:31 -0500
From: fedora fedora <fedorafans@gmail.com>
To: Robert Bonomi <bonomi@mail.r-bonomi.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Thanks, the thing is
How can i be sure even if a device blocks my ping , it might have policy
blocking ping at it at all.
On Sat, Sep 25, 2010 at 10:18 PM, Robert Bonomi <bonomi@mail.r-bonomi.com>wrote:
> > From nanog-bounces+bonomi=mail.r-bonomi.com@nanog.org Sat Sep 25
> 21:56:30 2010
> > Date: Sat, 25 Sep 2010 21:57:53 -0500
> > Subject: large icmp packet issue
> > From: fedora fedora <fedorafans@gmail.com>
> > To: nanog@nanog.org
> >
> > I am having problem getting ping to work to a specific destination host
> when
> > using large size icmp packet and i am hoping someone here can offer some
> > suggestion.
> >
> > With regular ping, i can ping this remote host without any problem, but
> if i
> > crank up the packet size to above 1500 (1500 still works), i won't get
> any
> > icmp reply.
> >
> > My first thought was this was a pmtu issue. but when I ran tcpdump on
> this
> > remote host, i saw the incoming ping requests and this host actually sent
> > back icmp replies, so it appears that there is some device in between
> > blocking these large size icmp reply packets.
> >
> > Here is the question, how can i find out which hop on the path is causing
> > this behavior?
>
> Did you consider doing a traceroute?
>
> And then pinging the intermediate machines? with the big packets, that is.
>
> you'll get a response from the 'near side' of the problem, but -not-
> from any machine on the far side of it.
>
> Ping with small packets first, to discovr machines that dont respond to
> pings at all.
>
>
