Network Operators and smurf

Jay R. Ashworth jra at
Fri Apr 24 23:06:14 UTC 1998

On Fri, Apr 24, 1998 at 06:06:50PM -0500, John A. Tamplin wrote:
> On Fri, 24 Apr 1998, Karl Denninger wrote:
> > Well, there is a simple knob for this:
> > If the Knob is turned "ON", then any packet from a source address which is 
> > not routed to the interface it came in on is dropped.
> > This works for static, dynamic, and all other kinds of routing.    It will
> > solve the problem and is trivial to implement - if any of the vendors care.
> It doesn't work for asymmetric routing as you describe it above. If you
> modify your criteria to be that there are no valid routes out that
> interface, you would only break transient routing conditions, but
> depending on how the router stores routes it may not be possible (or
> desirable due to memory requirements) to implement. 

Yeah, John, we know that.  But I've rarely seen a /32 with asymmetric
routing.  The vast majority (I speculate) of these problems happen on
the far side of border routers which are unlikely to be participating
in ASR, are they not?  How far down is it being used?

-- jra
Jay R. Ashworth                                                jra at
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