[6bone] non-global address space for IXs (was: 2001:478:: as /48)

[Stephane Bortzmeyer]

On Sunday 7 September 2003, at 1 h 14, 
Gert Doering <gert@space.net> wrote:

> > address space is not globally routed, it breaks PMTU-Disc, traceroute,
> > etc.
> 
> It does nothing of this, *unless* you're also doing reverse-path filtering
> on your external links 

Even if you do not filter incoming unsollicited ICMP, many networks filter 
incoming RFC 1918 packets and therefore you will lose the PMTU messages.

> It breaks pinging / tracerouting *to* a specific router on its IXP
> address, indeed, but not *through* the router, which is by far the
> most common usage.

It does break traceroute through the router. If two routers on the path use the same RFC 1918 address, imagine the difficulty of interpreting that traceroute output? Or of comparing two traceroutes?

I agree with Robert Kiessling <Robert.Kiessling@de.easynet.net> that non-announced - or announced-but-filtered - addresses are *less* a problem than RFC 1918, until people start filtering incoming packets whose IP source address is not in an announced block...