Re: Forwarding Packets With Link Local Destination Addresses

Toerless Eckert <tte@cs.fau.de> Thu, 07 January 2021 19:02 UTC

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Date: Thu, 7 Jan 2021 20:02:17 +0100
From: Toerless Eckert <tte@cs.fau.de>
To: Fred Baker <fredbaker.ietf@gmail.com>
Cc: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>, 6man@ietf.org
Subject: Re: Forwarding Packets With Link Local Destination Addresses
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On Thu, Jan 07, 2021 at 10:45:43AM -0800, Fred Baker wrote:
> On Jan 7, 2021, at 9:54 AM, Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org> wrote:
> > According to RFC 4291, ???routers must not forward any packets with Link-Local source or destination addresses to other links???.
> 
> This, of course, imposes a requirement that no routers I???m aware of carry out absent explicit configuration, which is to make a forwarding decision (in this case a filter) based on the source address.

The words are english. The sentence structure looks more german, but i still can't parse it.

I also thought we had (source/mask,dest/mask) forwarding for IPv6 multi-homing somehwere in Homenet at some point in time. Without explicit config, just to enable to use source address to steer packets towards the desired ISP exit point.

> Reverse forwarding lookups *might* accomplish this by associating link local addresses with the interface the packet it was received on, but that would only happen if reverse address lookups (normally associated with BCP 38) were enabled. 
> 
> So one could argue that RFC 4291 goes beyond its remit in this regard.

"beyond its remit" for mentioning source address ? 

Cheers
    toerless