[AusNOG] ICMP weirdness inside Internode's network

Karl Auer kauer at biplane.com.au
Fri Oct 28 16:51:32 EST 2011

On Fri, 2011-10-28 at 13:52 +1100, Julien Goodwin wrote:
> I was just debugging some IPv6 issues on a DSL session in MEL (all my side),
> when as one of the final actions I traced from my DSL in SYD and got * steps,
> but only on v4, not on v6.

I really apologise if this is all old news to you, and even more if you
actually know the topologies concerned and have discounted these
aspects, but just in case:

The IPv6 topology does not have to follow the IPv4 topology. The path of
one is not the path of the other (very Zen). The DNS can lie about that,
too, so names in traceroutes aren't a reliable indicator that a node the
IPv6 path appears to pass though a) is actually that node or b) is the
same node as the IPv4 path passes through. IPv4 and IPv6 being different
protocols, the same node may handle ICMPv6 and ICMPv4 differently, and
it's quite common for people to block ICMPv4 while not blocking ICMPv6.

Regards, K.

Karl Auer (kauer at biplane.com.au)                   +61-2-64957160 (h)
http://www.biplane.com.au/kauer/                   +61-428-957160 (mob)

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