Re: IPv6 path MTU discovery not working (large number of retransmited TCP data packets)

Gert Doering <[email protected]> Tue, 27 May 2025 15:17:44 +0200

Newsgroups	gmane.os.netbsd.devel.network
Message-ID	<[email protected]>

Hi,

On Tue, May 27, 2025 at 08:25:51AM -0400, Mouse wrote:
> > The number 1 rule for IPv6 routing is to *always* use a link local
> > address for the next hop, for everything.
> 
> Why?  I've been using globally-routed addresses for everything since
> 2002 and have never had any trouble I can attribute to the practice.
> What am I at risk of?

Religious prosecution.

There is no technical reason why a LLA or a GUA would work "better" or
"more robust".  There's benefits and drawbacks to both.  But in the end,
both resolve to a MAC address and that's where packets are sent to.

(Now, OSPFv3 is built to only ever think in terms of "LLA", while BGP
is built to mostly think in terms of "GUA" and when they tried to add
something-LLA, the end result was messy... - but neither has anything
to do with "where an end-host should point its gateway").

gert
-- 
"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             [email protected]

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