9fans - fans of the OS Plan 9 from Bell Labs
 help / color / mirror / Atom feed
From: "Russ Cox" <rsc@swtch.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] ip bug?
Date: Mon, 14 Jan 2008 19:02:38 -0500	[thread overview]
Message-ID: <20080115000239.A5DA21E8C1C@holo.morphisms.net> (raw)
In-Reply-To: <2306f876a0a7449b68b07751e72e37e1@quanstro.net>

> now if i
> 
> 	; ip/ping /net.alt/icmp!12.51.113.7!0
> 
> i usually get one packet back and snoopy reports

there are surely more packets than that.
for example, where are the arp packets that initially
discover that 12.51.113.7 is 0030488ef4fb?

i suspect that the machine is sending out an arp request
for 12.51.113.7 and getting back responses both from
the actual 12.51.113.7 as well as the 65 gateway.  
the 65 gateway responds a little bit later, so that you 
manage to get one ping off between getting the first
response and the second response.  if this is the case,
then your 65 gateway is wrong.

alternately, it could be that the 65 gateway is somehow
getting the ping traffic and responding with a 
"no route to host" and somehow that response is
poisoning the arp cache.  

snoopy -f 'icmp || arp' would tell for sure.
it would also be nice to see the output of netstat -i.

russ


  reply	other threads:[~2008-01-15  0:02 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-14 21:31 erik quanstrom
2008-01-15  0:02 ` Russ Cox [this message]
2008-01-15  0:50   ` erik quanstrom

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080115000239.A5DA21E8C1C@holo.morphisms.net \
    --to=rsc@swtch.com \
    --cc=9fans@cse.psu.edu \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).