Re: [v6ops] RFC4861 question - short prefixes in PIOs

[Mark Smith <[e-mail]>]

On Sat., 29 Jun. 2019, 02:32 Philip Homburg, <[e-mail]>
wrote:

> >Hairpin'ing all traffic through the advertising router when L=0 seems like
> >the only general solution.  But, I can imagine many situations where if a
> >Neighbour Cache entry somehow existed, then it could be used.
>
> Note that the router may send redirects. So in theory it is only the
> first packet to a neighbor that needs to go through the router.
>


You'd have to switch them off in this case,.

That has also been a common thing to do in IPv4 in general. I can't exactly
remember why, because it is so long ago that I learned to do it, however I
expect it is to stop packets being punted to the control plane for redirect
generation. Non-optimal forwarding or dropping, in particular in forwarding
hardware, is cheaper than optimal forwarding and control plane load of
generating redirects. It also probably creates a control plane DoS attack
vector.


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