Interim Policy proposal for IPv6 Address Assignment Policy for Internet Exchange Points

Pekka Savola wrote:
> On Fri, 31 Aug 2001, Gert Doering wrote:
> > On Fri, Aug 31, 2001 at 03:58:04PM +0300, Pekka Savola wrote:
> > > Care to explain how traceroute through these IX's is supposed to work, if
> > > the node performing traceroute, ping, or whatever, is not a small-scale
> > > customer (ie. default route) of the IX participants?
> >
> > For a traceroute *through* the IX you don't need the route to that /64.
> > It might get filtered if you do RPF filtering (but multihomed customers
> > usually don't, because it doesn't work), but reachability of the hosts
> > *behind* the IX is not a problem.
> 
> RPF is an additional issue, granted, but not the point here.
> 
> Traceroute will skip a hop or two, ie. those p-t-p links where these
> internal addresses are used; these might be crucial when debugging or
> tracing where the traffic goes.
> 
> This might make (depending on the topology) a 15 second wait for the magic
> '* * *' combination.
> 
> After and before these, it will continue in a normal fashion.  But boy,
> would this be annoying..

That depends on how your particular traceroute works.  The common approach is
to send packets (typically UDP to high-numbered ports) to the _destination_
address with increasing TTLs and look for the ICMP TTL Exceeded message to
come back from each intermediate hop -- no traceroute packets are addressed
_to_ the intermediate routers. So, unless you're explicitly filtering packets
sourced from unrouted address space (e.g. RPF), you'll still get a useful(?)
traceroute output.

James