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From: "Miquel van Smoorenburg" <miquels@cistron.nl>
To: linux-kernel@vger.kernel.org
Subject: Re: connectivity to bkbits.net?
Date: Thu, 28 Nov 2002 23:59:24 +0000 (UTC)	[thread overview]
Message-ID: <as6aks$amj$1@ncc1701.cistron.net> (raw)
In-Reply-To: <20021128211347.D27234@flint.arm.linux.org.uk>

In article <20021128211347.D27234@flint.arm.linux.org.uk>,
Russell King  <rmk@arm.linux.org.uk> wrote:
>On Thu, Nov 28, 2002 at 06:53:00PM +0200, Kai Henningsen wrote:
>> >From two or three traceroutes, that problem seems to be at the SGI end. I  
>> can't get to them either (nothing after the same IP as for you, at hop  
>> #17, some place at Genuity), but you are practically next door.
>
>Lesson #1 of firewalling: drop everything.
>Lesson #2 of firewalling: only accept what you absolutely have to.

Lesson#3 of firewalling: due to #1 and #2 most admins block
ICMP_UNREACH_NEEDFRAG as well (ICMP == ping == bad) breaking
path MTUd. http://alive.znep.com/~marcs/mtu/

Note that IPv6 has no fragmentation and pMTUd is mandatory.
Oh joy.

Mike.
-- 
They all laughed when I said I wanted to build a joke-telling machine.
Well, I showed them! Nobody's laughing *now*! -- acesteves@clix.pt


  reply	other threads:[~2002-11-28 23:52 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-11-28 16:25 Larry McVoy
2002-11-28 16:53 ` Kai Henningsen
2002-11-28 21:13   ` Russell King
2002-11-28 23:59     ` Miquel van Smoorenburg [this message]
2002-11-29  6:55       ` Kai Henningsen

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