Messages in this thread | | | From | "Miquel van Smoorenburg" <> | Subject | Re: connectivity to bkbits.net? | Date | Thu, 28 Nov 2002 23:59:24 +0000 (UTC) |
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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
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